1. cmd_status now validates session IDs against opencode session list
- Reports 'error: base session X not found in opencode' if missing
- Reports 'error: pm_agent session X not found in opencode' if missing
2. Test suite now uses isolated KUGETSU_DIR=/tmp/test-kugetsu-$$
- All tests use separate test directory instead of ~/.kugetsu
- Prevents test suite from corrupting real user data
- Cleanup removes test directory entirely
Fixes#148