chore: gitignore Claude Code harness runtime artifacts

.claude/scheduled_tasks.lock appears when ScheduleWakeup fires. It's a
runtime lock file owned by the Claude Code harness, not project source.
Add .claude/*.lock too so future harness artifacts in that directory
don't need their own gitignore entries.

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

.gitignore

@@ -6,6 +6,8 @@ design/dist/
 bin/gstack-global-discover
 .gstack/
 .claude/skills/
+.claude/scheduled_tasks.lock
+.claude/*.lock
 .agents/
 .factory/
 .kiro/