chore: gitignore .claude/worktrees

Per-session Claude Code checkouts live under .claude/worktrees/<slug>/
on the trunk; keep them out of git so the main checkout stays clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -2,4 +2,7 @@
 .terraform.*
 .DS_Store
 node_modules/
-.venv/
+.venv/
+
+# Claude Code worktrees (per-session checkouts under .claude/worktrees/<slug>/)
+.claude/worktrees/