Summary

• When AI mentions a file by bare name (e.g. __init__.py, index.js), the backend now searches the project tree via BFS instead of returning 404
• If exactly one match is found, the file opens automatically; if multiple matches exist, a disambiguation picker UI is shown
• Partial relative paths (e.g. src/main.tsx when the actual path is frontend/src/main.tsx) are also resolved by suffix-matching against the
  project tree
• BFS follows symlinks (fixes .claude/skills/*) and only skips node_modules, .git, dist, build
• Extensionless files like Dockerfile, Makefile, Procfile are recognized as clickable links in chat messages
• 404 errors show "File not found" instead of raw HTTP status
• Path separators are normalized for Windows compatibility

Test plan

• Click a bare filename in chat that exists once → auto-opens
• Click a bare filename with multiple matches (e.g. __init__.py) → picker shown, selecting one opens it
• Click a partial relative path (e.g. src/main.tsx) that doesn't match the root but exists deeper → auto-resolves
• Click a full relative path (server/index.js) → opens directly, no search
• Click a root file (package.json) → opens directly
• Click Dockerfile or Makefile in chat → highlighted as clickable, opens correctly
• Click a nonexistent filename → shows "File not found" error
• Picker is scrollable with long lists and has a close button