Add workspace adapter transaction contract

[Hisakazu333]

Summary

• add a concrete NekoBuddy workspace adapter transaction contract command covering workspace schema version, migration policy, receipt version, transaction state, failure recovery, and rollback blocking reasons
• make adapter import transaction-journaled, write versioned receipts with migration/transaction metadata, and add recover-import cleanup for failed imports
• update adapter tests and docs for schema/migration blocking, failed import recovery, and stable rollback blocking reasons

Tests

• npm run test:adapter
• npm run build
• npm run check:rust
• npm run test:security-audit
• git diff --check