feat(client): add 12 P3 tests — z-layer, entity lerp, Tyre additions (#493)
gdUnit4 tests covering:
- Z-layer ordering (4): floor below ysort, entities in ysort at z:0,
fog exact z_index values (Z_FOG=900, Z_FOG_ENTITIES=950), UI layers
- Entity lerp (3): snap on first appear, moves toward target,
converges within 0.3s at LERP_SPEED=12.0
- Tyre additions (5): recognition progress, facing rotation, lerp
weight scaling with delta, blob removal, LERP_SPEED constant guard
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>