feat: configurable paste collapse thresholds (TUI + CLI)

Adds two new config keys:
- paste_collapse_threshold (default: 5) — line count threshold for
  bracketed paste collapse in both TUI and CLI
- paste_collapse_threshold_fallback (default: 0, disabled) — same for
  the fallback heuristic in terminals without bracketed paste support

TUI frontend reads these from config.get full via applyDisplay/patchUiState.
CLI reads from self.config at paste-handling time.

Closes #5626
Related: #5623

ui-tui/src/app/interfaces.ts

@@ -105,6 +105,8 @@ export interface UiState {
   info: null | SessionInfo
   inlineDiffs: boolean
   mouseTracking: MouseTrackingMode
+  pasteCollapseLines: number
+
   sections: SectionVisibility
   showCost: boolean
   showReasoning: boolean

ui-tui/src/app/uiStore.ts

@@ -17,6 +17,7 @@ const buildUiState = (): UiState => ({
   info: null,
   inlineDiffs: true,
   mouseTracking: MOUSE_TRACKING,
+  pasteCollapseLines: 5,
   sections: {},
   showCost: false,
   showReasoning: false,

ui-tui/src/app/useComposerState.ts

@@ -8,7 +8,6 @@ import { useStore } from '@nanostores/react'
 import { useCallback, useMemo, useState } from 'react'
 
 import type { PasteEvent } from '../components/textInput.js'
-import { LARGE_PASTE } from '../config/limits.js'
 import type { ImageAttachResponse, InputDetectDropResponse } from '../gatewayTypes.js'
 import { useCompletion } from '../hooks/useCompletion.js'
 import { useInputHistory } from '../hooks/useInputHistory.js'
@@ -190,8 +189,9 @@ export function useComposerState({
       }
 
       const lineCount = cleanedText.split('\n').length
+      const pasteCollapseLines = getUiState().pasteCollapseLines
 
-      if (cleanedText.length < LARGE_PASTE.chars && lineCount < LARGE_PASTE.lines) {
+      if (pasteCollapseLines === 0 || lineCount < pasteCollapseLines) {
         return {
           cursor: cursor + cleanedText.length,
           value: value.slice(0, cursor) + cleanedText + value.slice(cursor)

ui-tui/src/app/useConfigSync.ts

@@ -142,6 +142,17 @@ const _voiceRecordKeyFromConfig = (cfg: ConfigFullResponse | null): ParsedVoiceR
   return raw ? parseVoiceRecordKey(raw) : DEFAULT_VOICE_RECORD_KEY
 }
 
+const _pasteCollapseLinesFromConfig = (cfg: ConfigFullResponse | null): number => {
+  if (!cfg?.config) return 5
+  const raw = cfg.config.paste_collapse_threshold
+  if (typeof raw === 'number' && Number.isFinite(raw) && raw >= 0) return Math.round(raw)
+  if (typeof raw === 'string') {
+    const n = parseInt(raw, 10)
+    if (Number.isFinite(n) && n >= 0) return n
+  }
+  return 5
+}
+
 /** Fetch ``config.get full`` and fan the result through ``applyDisplay``.
  *
  * Extracted so the mtime-reload path can be exercised by the test
@@ -188,6 +199,7 @@ export const applyDisplay = (
     indicatorStyle: normalizeIndicatorStyle(d.tui_status_indicator),
     inlineDiffs: d.inline_diffs !== false,
     mouseTracking: normalizeMouseTracking(d),
+    pasteCollapseLines: _pasteCollapseLinesFromConfig(cfg),
     sections: resolveSections(d.sections),
     showCost: !!d.show_cost,
     showReasoning: !!d.show_reasoning,

ui-tui/src/config/limits.ts

@@ -1,4 +1,4 @@
-export const LARGE_PASTE = { chars: 8000, lines: 80 }
+export const LARGE_PASTE = { lines: 5 }
 
 export const LIVE_RENDER_MAX_CHARS = 16_000
 export const LIVE_RENDER_MAX_LINES = 240

ui-tui/src/gatewayTypes.ts

@@ -82,7 +82,7 @@ export interface ConfigVoiceConfig {
 }
 
 export interface ConfigFullResponse {
-  config?: { display?: ConfigDisplayConfig; voice?: ConfigVoiceConfig }
+  config?: { display?: ConfigDisplayConfig; voice?: ConfigVoiceConfig; paste_collapse_threshold?: number }
 }
 
 export interface ConfigMtimeResponse {