chore(gitignore): exclude runtime artefacts

.claude/scheduled_tasks.lock and .claude/worktrees/ are per-session
runtime state — they were surfacing as untracked and should never be
committed (the latter is agent worktree state that belongs to whichever
session spawned it, per rules/worktree-boundaries.md).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -12,6 +12,10 @@
 .claude/sync-cache.json
 .claude/canvas/
 
+# Runtime artefacts (must never be tracked)
+.claude/scheduled_tasks.lock
+.claude/worktrees/
+
 # Backup files
 *.bak
 *~