chore: gitignore .claude/ (agent worktrees pollute lint + git add -A)

Co-Authored-By: Claude Opus 4.8 <[email protected]>

.gitignore

@@ -34,3 +34,8 @@ coverage/
 # The *.example templates ARE committed; the real files are not.
 infra/tofu/backend.hcl
 infra/tofu/.r2.env
+
+# Claude Code local scratch: agent worktrees + session state. Nothing here is tracked;
+# ignoring it keeps `git add -A` from staging embedded worktree repos and keeps the lint
+# stage (which scans untracked files) from tripping on .claude/worktrees/.
+.claude/