docs: refresh CLAUDE.md files and open.md to current code state

- Ui CLAUDE.md rewritten around the islands architecture (old
  MainWindow/TaskList/StatusBar VMs no longer exist)
- Worker: folder layout (Refine/, Lifecycle/Planning extras), full hub
  method/event surface, external MCP tool inventory
- Data: complete GitService operation list incl. commit-range diffs
- App: missing DI registrations; Tests: current test-area overview
- root: project list (Localization, Installer, six test projects) and
  honest docs index; plan.md/improvement-plan.md marked historical
- open.md: date bump + visual check for new diff viewer / attention band

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/ClaudeDo.Data/CLAUDE.md

@@ -35,7 +35,7 @@ All repositories use EF Core LINQ queries via `ClaudeDoDbContext`. The atomic `Q
 
 ## Git
 
-- **GitService** — async wrapper around git CLI (ProcessStartInfo, no shell). Operations: worktree add/remove, add all, commit (stdin for message), merge ff-only, rev-parse, diff-stat, has-changes, is-git-repo, `PreviewMergeAsync` (non-destructive mergeability check via `git merge-tree --write-tree`), `CountChangedFilesAsync`
+- **GitService** — async wrapper around git CLI (ProcessStartInfo, no shell). Worktree ops (add — serialized to avoid a commondir race —, remove, prune, list paths for branch), branch ops (current, list local, checkout, delete), staging/commit (status porcelain, add-all, add-path, commit via stdin), diffs (working tree, branch vs base, commit range `base..head` — used to show a merged task's diff after the worktree is gone —, per-file, diff-stat, committed files, has-changes), merge (ff-only, no-ff, abort, mid-merge detection, conflicted files, show-stage for conflict hunks), `PreviewMergeAsync` (non-destructive mergeability check via `git merge-tree --write-tree`), `CountChangedFilesAsync`, rev-parse, is-git-repo
 
 ## Schema