feat: add optional editable task titles

[jmalmo]

Related GitHub Issue

Closes: #8366

Description

This feature introduces editable titles for tasks, allowing users to label active work, persist those titles into task history, and search them—while providing a settings toggle and aligning the visual treatment across the UI.

Server ↔️ Webview plumbing

• Expand HistoryItem with title and update ClineProvider.updateTaskHistory to merge partial updates so existing titles survive incremental syncs; explicitly allow undefined to clear a title.
• Add a setTaskTitle branch in webviewMessageHandler that normalizes/dedupes task IDs, trims/sanitizes the incoming title, skips no-op updates, persists via updateTaskHistory, and re-syncs the webview state.
• Thread a persisted taskTitlesEnabled flag through extension messages/state and surface it to the webview context so both chat and history components react to the toggle.

Webview UI

• Chat header (TaskHeader.tsx): introduce an inline editing experience (VS Code styled input, focus/keyboard handling, hover pencil) gated by the feature flag; when a title exists, display the text with standard weight instead of bolding.
• History list (TaskItem.tsx): prefer titles when enabled, apply shared truncation/highlight behaviour, and render HTML highlights without the previous font-semibold class so edited titles visually match default entries.
• History search (useTaskSearch.ts): augment FZF selector to search titles + task prompts, split highlight ranges between title/task, and retain results ordering across sort modes.

Settings & Telemetry

• Add a “Task titles” checkbox in UISettings that toggles the new flag and emits ui_settings_task_titles_enabled_changed.
• Ensure initial extension state defaults opt-out and hydrate from cached settings.

Tests & Localization

• Extend chat header tests to cover editing workflows and disabled states.
• Update history item and search hooks tests to assert new title/highlight paths and the removal of bold styling.
• Add localisation strings for add/edit title affordances and the new settings copy.

Test Procedure

• pnpm vitest webview-ui/src/components/chat/__tests__/TaskHeader.spec.tsx
• pnpm vitest webview-ui/src/components/history/__tests__/TaskItem.spec.tsx
• pnpm vitest webview-ui/src/components/history/__tests__/useTaskSearch.spec.tsx
• (Optional manual) enable “Task titles” in Settings → UI and verify titles can be created/edited in the chat header and task history list without bold styling

Screenshots / Videos

Documentation Updates

• [ x] No documentation updates are required.
• Yes, documentation updates are required.

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Important

Introduces editable task titles feature with UI support and settings toggle, including backend logic and tests.

• Behavior:
  • Adds editable task titles feature, controlled by taskTitlesEnabled flag in global-settings.ts and history.ts.
  • Updates ClineProvider to handle task title updates and sync with webview.
  • Adds setTaskTitle and setTaskTitlesEnabled message types in webviewMessageHandler.
• UI:
  • TaskHeader.tsx: Implements inline editing for task titles with a pencil icon, focus handling, and keyboard shortcuts.
  • TaskItem.tsx: Displays task titles if enabled, with fallback to task text.
  • UISettings.tsx: Adds checkbox to toggle task titles feature.
• Tests:
  • Extends tests in TaskHeader.spec.tsx, TaskItem.spec.tsx, and useTaskSearch.spec.tsx to cover new title editing and display logic.
• Localization:
  • Adds strings for task title editing in chat.json and settings.json.

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[roomote]

Review Complete ✅

I've completed a thorough review of this PR. After examining the implementation, tests, and integration points, I found no issues that require changes.

Summary

This PR successfully implements editable task titles with:

• Proper title preservation logic in updateTaskHistory
• Feature flag gating throughout the UI
• Correct search integration with title highlighting
• Comprehensive test coverage
• Consistent styling (titles render without bold as requested)
• Complete localization across all supported languages

The implementation is production-ready and can be merged.