refactor(tui): store-driven turn state + slash registry + module split

Hoist turn state from a 286-line hook into $turnState atom + turnController
singleton. createGatewayEventHandler becomes a typed dispatch over the
controller; its ctx shrinks from 30 fields to 5. Event-handler refs and 16
threaded actions are gone.

Fold three createSlash*Handler factories into a data-driven SlashCommand[]
registry under slash/commands/{core,session,ops}.ts. Aliases are data;
findSlashCommand does name+alias lookup. Shared guarded/guardedErr combinator
in slash/guarded.ts.

Split constants.ts + app/helpers.ts into config/ (timing/limits/env),
content/ (faces/placeholders/hotkeys/verbs/charms/fortunes), domain/ (roles/
details/messages/paths/slash/viewport/usage), protocol/ (interpolation/paste).

Type every RPC response in gatewayTypes.ts (26 new interfaces); drop all
`(r: any)` across slash + main app.

Shrink useMainApp from 1216 -> 646 lines by extracting useSessionLifecycle,
useSubmission, useConfigSync. Add <Fg> themed primitive and strip ~50
`as any` color casts.

Tests: 50 passing. Build + type-check clean.

ui-tui/src/domain/messages.ts

@@ -0,0 +1,102 @@
+import { LONG_MSG } from '../config/limits.js'
+import { buildToolTrailLine, fmtK } from '../lib/text.js'
+import type { Msg, SessionInfo } from '../types.js'
+
+interface ImageMeta {
+  height?: number
+  token_estimate?: number
+  width?: number
+}
+
+interface TranscriptRow {
+  context?: string
+  name?: string
+  role?: string
+  text?: string
+}
+
+export const introMsg = (info: SessionInfo): Msg => ({ info, kind: 'intro', role: 'system', text: '' })
+
+export const imageTokenMeta = (info: ImageMeta | null | undefined) =>
+  [
+    info?.width && info.height ? `${info.width}x${info.height}` : '',
+    typeof info?.token_estimate === 'number' && info.token_estimate > 0 ? `~${fmtK(info.token_estimate)} tok` : ''
+  ]
+    .filter(Boolean)
+    .join(' · ')
+
+export const userDisplay = (text: string): string => {
+  if (text.length <= LONG_MSG) {
+    return text
+  }
+
+  const first = text.split('\n')[0]?.trim() ?? ''
+  const words = first.split(/\s+/).filter(Boolean)
+  const prefix = (words.length > 1 ? words.slice(0, 4).join(' ') : first).slice(0, 80)
+
+  return `${prefix || '(message)'} [long message]`
+}
+
+export const toTranscriptMessages = (rows: unknown): Msg[] => {
+  if (!Array.isArray(rows)) {
+    return []
+  }
+
+  const result: Msg[] = []
+  let pendingTools: string[] = []
+
+  for (const row of rows) {
+    if (!row || typeof row !== 'object') {
+      continue
+    }
+
+    const { context, name, role, text } = row as TranscriptRow
+
+    if (role === 'tool') {
+      pendingTools.push(buildToolTrailLine(name ?? 'tool', context ?? ''))
+
+      continue
+    }
+
+    if (typeof text !== 'string' || !text.trim()) {
+      continue
+    }
+
+    if (role === 'assistant') {
+      const msg: Msg = { role, text }
+
+      if (pendingTools.length) {
+        msg.tools = pendingTools
+        pendingTools = []
+      }
+
+      result.push(msg)
+
+      continue
+    }
+
+    if (role === 'user' || role === 'system') {
+      pendingTools = []
+      result.push({ role, text })
+    }
+  }
+
+  return result
+}
+
+export function fmtDuration(ms: number) {
+  const total = Math.max(0, Math.floor(ms / 1000))
+  const hours = Math.floor(total / 3600)
+  const mins = Math.floor((total % 3600) / 60)
+  const secs = total % 60
+
+  if (hours > 0) {
+    return `${hours}h ${mins}m`
+  }
+
+  if (mins > 0) {
+    return `${mins}m ${secs}s`
+  }
+
+  return `${secs}s`
+}