chore: gitignore .claude/ local agent state

.claude/ holds settings.local.json and a live git worktree (~1.4MB) whose
metadata embeds machine-local absolute paths. It was showing up as untracked
noise in every status; ignoring it is correct, committing it would not be.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitignore

@@ -45,3 +45,7 @@ __pycache__/
 .venv/
 .DS_Store
 .idea/
+
+# Claude Code local state: settings.local.json plus a live git worktree.
+# Never commit - it embeds machine-local absolute paths.
+.claude/