Proves that previously-unreachable atlas slots become reachable
via the cell-tile material path: slot 0 isolated (t3), slot 1 end
with correct rotations (t4), slot 4 straight (t5), slot 5
tee_open (t6), slot 8 cross_open (t7).
Upgrades write_test.map.json to schema_version 3 with material
and vertices fields on surface so cell_material_slot + set_vertex
resolve correctly in the tests.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Migrates the test-lib content authored alongside lib-core.maps v0.2.0
into its canonical role=test location. Covers packed-u32 GID encode/
decode round-trip, v1 to v2 schema upgrade, schema-v2 validation,
multi-layer load, multi-atlas resolution, per-layer tile lookup with
tile_at backwards-compat, gameplay queries (is_walkable, blocks_walk,
blocks_sight), layer iteration around the entity slot, and v1 JSON
auto-migration on load. 367 assertions total when run via the engine
test-libs harness.
New fixtures: maps/demo_v2.map.json (4x4 multi-layer with roof) and
assets/tiles/walls_tilemap.tilemap.json (second atlas with wall tiles).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
