Validate every element count against the remaining payload before
reserving, reject trailing bytes, type-check envelope fields, bound the
untrusted uncompressed_bytes hint, read the magic little-endian, and
convert legacy JSON type errors into Result errors instead of throwing.
Replace 960+ MB raw JSON snapshot serialization in MetadataKgTopologyArtifactStore with a compact, string-interned binary format compressed with Zstandard.
- Add yams::topology::serializeTopologyBatchBinary and deserializeTopologyBatchBinary with integer length packing and string deduplication.
- Wrap binary payload in a backward-compatible JSON envelope with format: zstd_binary_v1 and base64 encoded payload, maintaining SQLite json_valid(properties) == 1.
- Fall back gracefully to legacy raw JSON deserializer when reading pre-existing uncompressed snapshots.
- Add Catch2 unit test suite verifying binary roundtrip fidelity, compression ratio, backward-compatibility with legacy JSON snapshots, and corrupted payload resilience.
Signed-off-by: trvon <me@trevon.dev>
