Tyre #1: Added Rust-generated input_batch_two.msgpack fixture for
bidirectional D-030 Layer 1 symmetry (Vec<PlayerInput>).
Tyre #2: Added all_fixtures_deserialize Rust test that reads every
.msgpack fixture and verifies it deserializes (corruption guard).
Hoshe #3: Added test_decode_snapshot_malformed_entities_counted test
verifying the decode_errors counter on D-010 boundary violations.
45 client tests, 54 server tests pass.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
