Strengthen seqNo lock regression test

[zakoverflow]

Summary

• replace the CRC-stamping lock regression check with one that verifies seqNo advances before the Notecard unlock hook returns
• start a nested unlocked transaction from the unlock hook and assert it sees firstSeq + 1, which would fail if seqNo++ moved after unlock

Testing

• docker run --rm -v /home/ubuntu/.openclaw/workspace/note-c:/note-c -w /note-c ghcr.io/blues/note_c_ci:latest bash -lc 'cmake --build build --target NoteTransaction_test -j && ./build/test/NoteTransaction_test && ctest --test-dir build --output-on-failure'\n- 166/166 unit tests passed\n\n## Architecture docs\n- No architecture doc update needed; this is test-only coverage for the existing locking behavior.