Summary

• Reuse an existing corrupt Kanban DB backup when the bytes match
• Avoid creating backup landfill on repeated dispatcher probes
• Add regression coverage for repeated corrupt DB probes

Test Plan

• python -m pytest tests/hermes_cli/test_kanban_db.py::test_init_db_refuses_corrupt_existing_file tests/hermes_cli/test_kanban_db.py::test_connect_refuses_corrupt_existing_file tests/hermes_cli/test_kanban_db.py::test_repeated_corrupt_db_probe_reuses_existing_backup tests/hermes_cli/test_kanban_db.py::test_locked_healthy_db_does_not_classify_as_corrupt -q -o 'addopts='