Protocol v17: add state_hash (desync detection) and sim_errors
(structured error reporting) to ObserverSnapshot. Add SimError,
SimErrorKind, SimErrorBuffer types. Wrap main loop app.update() in
catch_unwind — on panic, send a final SimError snapshot before exit.
Report recoverable deserialization errors to client via SimErrorBuffer.
Compute per-tick state hash from player position + NPC count + tick.
Update all test fixtures and golden files for protocol v17.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Updates all client-side msgpack test fixtures and server test
harnesses to include the new triangle_crisis_events field added
in protocol v16.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Five new .msgpack fixtures: snapshot_minimal, snapshot_full,
player_input_move, player_input_interact, malformed. Rust generator in
gen_fixtures.rs, 7 Rust validation tests in serialization.rs, GDScript
cross-language test in test_ipc_fixtures.gd (22 assertions).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>