chore: ignore local worktrees directory

Add .worktrees/ to .gitignore to prevent accidental tracking of isolated worktree files.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitignore

@@ -14,3 +14,6 @@ data/*.db-shm
 .idea/
 .vscode/
 *.swp
+
+# Local worktrees
+.worktrees/