Syntax highlighting & code viewer:
- Add shiki for syntax-highlighted fenced code blocks in chat messages
- New SyntaxBlock component (lazy shiki, dual light/dark theme)
- New CodeViewer for workspace file panel (routes code files via isCodeFile())
- API routes (browse-file, virtual-file) now return "code" type for known extensions
Diff rendering:
- New DiffCard component for rendering unified diffs with add/remove colors
- diff-blocks.ts parser to extract fenced blocks from markdown
- Chain-of-thought tool steps show inline diffs for edit/write tools
(synthetic from old_string/new_string or direct from tool output)
- Agent runner passes through diff/firstChangedLine from edit tool results
- Document view handles diff blocks alongside report blocks
Rich chat editor (Tiptap):
- Replace plain textarea with Tiptap-based ChatEditor
- File mention extension (@-mention files with autocomplete dropdown)
- File mention list with keyboard navigation and search via suggest-files API
- New suggest-files API endpoint for fuzzy file search
File search & navigation:
- FileSearch component in workspace sidebar (debounced search, keyboard nav)
- Search results navigate sidebar to file location and open in panel
- File picker modal for browsing/selecting workspace files
Drag & drop:
- File tree nodes support native HTML5 drag (application/x-file-mention)
for cross-component drops (e.g. dragging files into chat editor)
Chat attachments reworked:
- Switch from browser File objects to path-based references (name + path)
- Simplified attachment strip (no media previews, shows shortened paths)
Also adds software-engineering skill and related CSS for code blocks/shiki.
