feat: source-bind query preview cleanup restore dry run

[cafitac]

Summary

• Add source database fingerprint metadata to query-preview cleanup rollback artifacts/manifests.
• Make restore dry-run fail closed with source_database_mismatch when the rollback artifact was created for a different target database.
• Keep restore dry-run read-only, live restore unavailable, and stdout free of raw query-preview values.

Test Plan

• uv run pytest tests/test_cli.py::test_python_module_cli_dogfood_query_preview_cleanup_restore_dry_run_validates_artifact_without_mutation_or_leaks tests/test_cli.py::test_python_module_cli_dogfood_query_preview_cleanup_restore_dry_run_blocks_source_database_mismatch -q
• uv run pytest tests/ -q
• uv run ruff check src tests
• git diff --check
• restore fingerprint smoke under /tmp/agent-memory-restore-fingerprint-smoke

Safety notes

• This does not enable live restore.
• This does not enable broad G4 apply mode.
• Rollback artifacts remain private/local because they contain raw query-preview values.
• Restore dry-run output reports only hash/count/path-basename metadata.