refactor(desktop): colocate hook/component families into scoped folders

Single-scoped helpers/sub-files were sitting flat in shared/grab-bag dirs.
Fold each family into its own folder (index = the export, dir resolution keeps
public import paths intact), dropping the now-redundant filename prefix:

- session/hooks/use-prompt-actions.ts (+ -utils, + tests)
  -> use-prompt-actions/{index,utils}.ts (+ tests)
- components/assistant-ui/thread* + assistant/system/user message renderers
  -> assistant-ui/thread/{index,content,status,message-parts,timestamp,types,
     list,timeline,timeline-data,assistant-message,system-message,user-message,
     user-edit-composer,user-message-text} (+ tests)
- components/assistant-ui/tool-fallback(+model)/tool-approval
  -> assistant-ui/tool/{fallback,fallback-model,approval} (+ tests)

Pure move + import rewrites; no behaviour change. App-wide shared primitives
(markdown-text, directive-text, tooltip-icon-button, clarify-tool, ansi-text,
message-render-boundary) stay flat. desktop-controller intentionally left in
app/ (route root; foldering would churn ~80 relative imports for no gain).

apps/desktop/src/app/session/hooks/use-prompt-actions/index.test.tsx

@@ -8,7 +8,7 @@ import { $composerAttachments, type ComposerAttachment } from '@/store/composer'
 import { $busy, $connection, $messages, $sessions, setSessions } from '@/store/session'
 import type { SessionInfo } from '@/types/hermes'
 
-import { uploadComposerAttachment, usePromptActions } from './use-prompt-actions'
+import { uploadComposerAttachment, usePromptActions } from '.'
 
 vi.mock('@/hermes', () => ({
   getProfiles: vi.fn(async () => ({ profiles: [] })),

apps/desktop/src/app/session/hooks/use-prompt-actions/index.ts

@@ -72,7 +72,7 @@ import type {
   SessionSteerResponse,
   SessionTitleResponse,
   SlashExecResponse
-} from '../../types'
+} from '../../../types'
 
 import {
   _submitInFlight,
@@ -93,7 +93,7 @@ import {
   visibleUserIndexAtOrdinal,
   visibleUserOrdinal,
   withSessionBusyRetry
-} from './use-prompt-actions-utils'
+} from './utils'
 
 interface HandoffResult {
   ok: boolean

apps/desktop/src/app/session/hooks/use-prompt-actions/utils.test.ts

@@ -15,7 +15,7 @@ import {
   slashStatusText,
   visibleUserIndexAtOrdinal,
   visibleUserOrdinal
-} from './use-prompt-actions-utils'
+} from './utils'
 
 describe('isSessionIdCandidate', () => {
   it('accepts the timestamped and hex id forms', () => {

apps/desktop/src/components/assistant-ui/clarify-tool.tsx

@@ -13,7 +13,7 @@ import {
   useState
 } from 'react'
 
-import { ToolFallback } from '@/components/assistant-ui/tool-fallback'
+import { ToolFallback } from '@/components/assistant-ui/tool/fallback'
 import { Button } from '@/components/ui/button'
 import { Kbd } from '@/components/ui/kbd'
 import { Textarea } from '@/components/ui/textarea'
@@ -25,7 +25,7 @@ import { $clarifyRequest, clearClarifyRequest } from '@/store/clarify'
 import { $gateway } from '@/store/gateway'
 import { notifyError } from '@/store/notifications'
 
-import { selectMessageRunning } from './tool-fallback-model'
+import { selectMessageRunning } from './tool/fallback-model'
 
 interface ClarifyArgs {
   question?: string

apps/desktop/src/components/assistant-ui/thread/assistant-message.tsx

@@ -13,10 +13,10 @@ import {
   contentHasVisibleText,
   messageContentText,
   pickPrimaryPreviewTarget
-} from '@/components/assistant-ui/thread-content'
-import { MESSAGE_PARTS_COMPONENTS } from '@/components/assistant-ui/thread-message-parts'
-import { StreamStallIndicator } from '@/components/assistant-ui/thread-status'
-import { formatMessageTimestamp } from '@/components/assistant-ui/thread-timestamp'
+} from '@/components/assistant-ui/thread/content'
+import { MESSAGE_PARTS_COMPONENTS } from '@/components/assistant-ui/thread/message-parts'
+import { StreamStallIndicator } from '@/components/assistant-ui/thread/status'
+import { formatMessageTimestamp } from '@/components/assistant-ui/thread/timestamp'
 import { TooltipIconButton } from '@/components/assistant-ui/tooltip-icon-button'
 import { PreviewAttachment } from '@/components/chat/preview-attachment'
 import { Codicon } from '@/components/ui/codicon'

apps/desktop/src/components/assistant-ui/thread/block-direction.test.tsx

@@ -10,7 +10,7 @@ import { AssistantRuntimeProvider, type ThreadMessage, useExternalStoreRuntime }
 import { render, screen } from '@testing-library/react'
 import { describe, expect, it, vi } from 'vitest'
 
-import { Thread } from './thread'
+import { Thread } from '.'
 
 const createdAt = new Date('2026-06-01T00:00:00.000Z')
 

apps/desktop/src/components/assistant-ui/thread/content.test.ts

@@ -6,7 +6,7 @@ import {
   messageContentText,
   partText,
   pickPrimaryPreviewTarget
-} from './thread-content'
+} from './content'
 
 describe('partText', () => {
   it('returns plain strings as-is', () => {

apps/desktop/src/components/assistant-ui/thread/index.tsx

@@ -1,17 +1,17 @@
 import { type FC, useCallback, useMemo, useState } from 'react'
 
-import { AssistantMessage } from '@/components/assistant-ui/assistant-message'
-import { SystemMessage } from '@/components/assistant-ui/system-message'
-import { ThreadMessageList } from '@/components/assistant-ui/thread-list'
+import { AssistantMessage } from '@/components/assistant-ui/thread/assistant-message'
+import { ThreadMessageList } from '@/components/assistant-ui/thread/list'
 import {
   BackgroundResumeNotice,
   CenteredThreadSpinner,
   ResponseLoadingIndicator
-} from '@/components/assistant-ui/thread-status'
-import { ThreadTimeline } from '@/components/assistant-ui/thread-timeline'
-import { type RestoreMessageTarget } from '@/components/assistant-ui/thread-types'
-import { UserEditComposer } from '@/components/assistant-ui/user-edit-composer'
-import { UserMessage } from '@/components/assistant-ui/user-message'
+} from '@/components/assistant-ui/thread/status'
+import { SystemMessage } from '@/components/assistant-ui/thread/system-message'
+import { ThreadTimeline } from '@/components/assistant-ui/thread/timeline'
+import { type RestoreMessageTarget } from '@/components/assistant-ui/thread/types'
+import { UserEditComposer } from '@/components/assistant-ui/thread/user-edit-composer'
+import { UserMessage } from '@/components/assistant-ui/thread/user-message'
 import { Intro, type IntroProps } from '@/components/chat/intro'
 import { ConfirmDialog } from '@/components/ui/confirm-dialog'
 import type { HermesGateway } from '@/hermes'

apps/desktop/src/components/assistant-ui/thread/list.tsx

@@ -24,7 +24,7 @@ import {
 } from '@/store/thread-scroll'
 import { isSecondaryWindow } from '@/store/windows'
 
-import { MessageRenderBoundary } from './message-render-boundary'
+import { MessageRenderBoundary } from '../message-render-boundary'
 
 type ThreadMessageComponents = ComponentProps<typeof ThreadPrimitive.MessageByIndex>['components']
 

apps/desktop/src/components/assistant-ui/thread/message-parts.tsx

@@ -3,7 +3,7 @@ import { type ComponentProps, type FC, type ReactNode, useEffect, useRef, useSta
 
 import { ClarifyTool } from '@/components/assistant-ui/clarify-tool'
 import { MarkdownText, MarkdownTextContent } from '@/components/assistant-ui/markdown-text'
-import { ToolFallback, ToolGroupSlot } from '@/components/assistant-ui/tool-fallback'
+import { ToolFallback, ToolGroupSlot } from '@/components/assistant-ui/tool/fallback'
 import { useElapsedSeconds } from '@/components/chat/activity-timer'
 import { ActivityTimerText } from '@/components/chat/activity-timer-text'
 import { DisclosureRow } from '@/components/chat/disclosure-row'

apps/desktop/src/components/assistant-ui/thread/streaming.test.tsx

@@ -3,7 +3,7 @@ import { act, fireEvent, render, screen, waitFor, within } from '@testing-librar
 import { useEffect, useState } from 'react'
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 
-import { Thread } from './thread'
+import { Thread } from '.'
 
 const createdAt = new Date('2026-05-01T00:00:00.000Z')
 

apps/desktop/src/components/assistant-ui/thread/system-message.tsx

@@ -1,7 +1,7 @@
 import { MessagePrimitive, useAuiState } from '@assistant-ui/react'
 import { type FC } from 'react'
 
-import { messageContentText } from '@/components/assistant-ui/thread-content'
+import { messageContentText } from '@/components/assistant-ui/thread/content'
 import { Codicon } from '@/components/ui/codicon'
 import { LinkifiedText } from '@/lib/external-link'
 import { cn } from '@/lib/utils'

apps/desktop/src/components/assistant-ui/thread/timeline-data.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest'
 
-import { activeTimelineIndex, deriveTimelineEntries, timelinePreview } from './thread-timeline-data'
+import { activeTimelineIndex, deriveTimelineEntries, timelinePreview } from './timeline-data'
 
 describe('timelinePreview', () => {
   it('collapses whitespace to a single line', () => {

apps/desktop/src/components/assistant-ui/thread/timeline.tsx

@@ -9,7 +9,7 @@ import {
   deriveTimelineEntries,
   type TimelineEntry,
   type TimelineSourceMessage
-} from './thread-timeline-data'
+} from './timeline-data'
 
 const MIN_ENTRIES = 4
 const VIEWPORT = '[data-slot="aui_thread-viewport"]'

apps/desktop/src/components/assistant-ui/thread/timestamp.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest'
 
-import { formatMessageTimestamp } from './thread-timestamp'
+import { formatMessageTimestamp } from './timestamp'
 
 const labels = {
   today: (time: string) => `Today at ${time}`,

apps/desktop/src/components/assistant-ui/thread/user-edit-composer.tsx

@@ -52,7 +52,7 @@ import {
   USER_ACTION_ICON_BUTTON_CLASS,
   USER_ACTION_ICON_SIZE,
   USER_BUBBLE_BASE_CLASS
-} from '@/components/assistant-ui/user-message'
+} from '@/components/assistant-ui/thread/user-message'
 import { Codicon } from '@/components/ui/codicon'
 import type { HermesGateway } from '@/hermes'
 import { useI18n } from '@/i18n'

apps/desktop/src/components/assistant-ui/thread/user-message-edit.test.tsx

@@ -13,7 +13,7 @@ import { describe, expect, it, vi } from 'vitest'
 
 import { useIncrementalExternalStoreRuntime } from '@/lib/incremental-external-store-runtime'
 
-import { Thread } from './thread'
+import { Thread } from '.'
 
 const createdAt = new Date('2026-05-01T00:00:00.000Z')
 

apps/desktop/src/components/assistant-ui/thread/user-message.tsx

@@ -2,9 +2,9 @@ import { ActionBarPrimitive, BranchPickerPrimitive, MessagePrimitive, useAuiStat
 import { type FC, type ReactNode, useCallback, useRef, useState } from 'react'
 
 import { DirectiveContent } from '@/components/assistant-ui/directive-text'
-import { messageAttachmentRefs, messageContentText } from '@/components/assistant-ui/thread-content'
-import { type RestoreMessageTarget } from '@/components/assistant-ui/thread-types'
-import { UserMessageText } from '@/components/assistant-ui/user-message-text'
+import { messageAttachmentRefs, messageContentText } from '@/components/assistant-ui/thread/content'
+import { type RestoreMessageTarget } from '@/components/assistant-ui/thread/types'
+import { UserMessageText } from '@/components/assistant-ui/thread/user-message-text'
 import { Codicon } from '@/components/ui/codicon'
 import { useResizeObserver } from '@/hooks/use-resize-observer'
 import { useI18n } from '@/i18n'

apps/desktop/src/components/assistant-ui/tool/approval-group.test.tsx

@@ -7,7 +7,7 @@ import { $activeSessionId } from '@/store/session'
 import { clearDismissedToolRows } from '@/store/tool-dismiss'
 import { $toolDisclosureStates } from '@/store/tool-view'
 
-import { Thread } from './thread'
+import { Thread } from '../thread'
 
 // Regression coverage for the "approval must never be buried" bug. Tools now
 // render as a flat list (no collapsible "N steps" group), so a pending tool's

apps/desktop/src/components/assistant-ui/tool/approval.test.tsx

@@ -6,8 +6,8 @@ import { $gateway } from '@/store/gateway'
 import { $approvalRequest, clearAllPrompts, setApprovalRequest } from '@/store/prompts'
 import { $activeSessionId } from '@/store/session'
 
-import { PendingApprovalFallback, PendingToolApproval } from './tool-approval'
-import type { ToolPart } from './tool-fallback-model'
+import { PendingApprovalFallback, PendingToolApproval } from './approval'
+import type { ToolPart } from './fallback-model'
 
 // Radix's DropdownMenu touches pointer-capture + scrollIntoView, which jsdom
 // doesn't implement; stub them so the menu can open in tests.

apps/desktop/src/components/assistant-ui/tool/approval.tsx

@@ -27,7 +27,7 @@ import {
   registerApprovalInlineAnchor
 } from '@/store/prompts'
 
-import type { ToolPart } from './tool-fallback-model'
+import type { ToolPart } from './fallback-model'
 
 // Inline approval control. Rendered as a compact button strip
 // under the pending tool row that raised the approval (the row already shows

apps/desktop/src/components/assistant-ui/tool/fallback-model.test.ts

@@ -9,7 +9,7 @@ import {
   inlineDiffFromResult,
   MAX_TOOL_RENDER_CHARS,
   type ToolPart
-} from './tool-fallback-model'
+} from './fallback-model'
 
 const part = (overrides: Partial<ToolPart>): ToolPart => ({
   args: {},

apps/desktop/src/components/assistant-ui/tool/fallback.tsx

@@ -30,7 +30,7 @@ import { $toolInlineDiffs } from '@/store/tool-diffs'
 import { $toolRowDismissed, dismissToolRow } from '@/store/tool-dismiss'
 import { $toolDisclosureOpen, $toolViewMode, setToolDisclosureOpen } from '@/store/tool-view'
 
-import { PendingToolApproval } from './tool-approval'
+import { PendingToolApproval } from './approval'
 import {
   buildToolView,
   clampForDisplay,
@@ -48,7 +48,7 @@ import {
   toolPartDisclosureId,
   type ToolStatus,
   type ToolTitleAction
-} from './tool-fallback-model'
+} from './fallback-model'
 
 // `true` when a ToolEntry is rendered inside an embedding wrapper that owns
 // the per-row chrome (timer / preview). The flat ToolGroupSlot sets this

apps/desktop/src/components/prompt-overlays.tsx

@@ -3,7 +3,7 @@
 import { useStore } from '@nanostores/react'
 import { type FormEvent, useCallback, useEffect, useState } from 'react'
 
-import { PendingApprovalFallback } from '@/components/assistant-ui/tool-approval'
+import { PendingApprovalFallback } from '@/components/assistant-ui/tool/approval'
 import { Button } from '@/components/ui/button'
 import {
   Dialog,