feat: migrate quilter rendering to Bevy TilemapChunk

Replaces the CPU pixel-baking quilter system (QuiltCache, TerrainSprite,
pixel_buffers) with Bevy's native TilemapChunk GPU-index-lookup API.

Architecture:
- TilemapChunk entities replace TerrainSprite entities per (chunk, z, layer)
- Tileset PNG stacked vertically as texture_2d_array (11 rows: 6 floor + 5 fixture)
- populate_chunk_tiles reads TileMap HashMap directly; no ECS FloorTile entities
- Chunk spawn deferred to apply_terrain_blobs (after TileMap data exists)
- Dirty key system triggers repopulate on occlusion/camera-z changes

Bug fixes:
- populate_chunk_tiles: add chunk_pos offset to world tile lookups (was always (0,0))
- spawn_tilemap_chunks: offset Transform by -TILE_SIZE/2 (tile-centre vs bottom-left)
- spawn_tilemap_chunks: AlphaMode2d::Blend (was Opaque, blocking DF fade)
- update_tilemap_chunk_visibility: actually mutate Visibility (was read-only)
- handle_tile_occlusion_updates: mark dirty keys inline (was double-reading events)
- TilemapChunkSpawner: deduplicate pending queue and guard stale registry

Performance:
- ~115K FloorTile ECS entities eliminated
- GPU memory: O(tile_data) instead of O(CHUNK_TILES² × z_levels × pixel_bytes)
- Z-scroll: only TilemapChunkTileData repopulates (no entity re-spawn)
- Benchmarks via TilemapBenchmark resource (F9 to report)

src/world/mod.rs

@@ -14,18 +14,19 @@ pub mod generation;
 pub mod textures;
 pub mod tiles;
 
-// Re-export commonly used items
 pub use chunks::management::*;
 pub use textures::management::*;
 pub use tiles::{prefabs::*, rendering::*, visibility::*};
 
-// Plugin
 pub struct WorldPlugin;
 
 impl Plugin for WorldPlugin {
     fn build(&self, app: &mut App) {
         app.init_resource::<ChunkMap>()
             .init_resource::<TerrainBlobStorage>()
+            .init_resource::<tiles::TilemapBenchmark>()
+            .init_resource::<tiles::TilemapChunkRegistry>()
+            .init_resource::<tiles::TilemapChunkSpawner>()
             .add_message::<GenerateChunkEvent>()
             .add_message::<ChunkTerrainEvent>()
             .add_message::<ChunkWeatheringAndPrecipitationEvent>()
@@ -37,19 +38,15 @@ impl Plugin for WorldPlugin {
             .add_systems(
                 FixedUpdate,
                 (
-                    // === CHUNK LOADING PIPELINE ===
                     handle_chunk_events,
                     update_chunk_connectivity,
-
-                    // === CHUNK GENERATION (triggered by events above) ===
+                    tiles::despawn_tilemap_chunks,
                     spawn_terrain_tasks,
                     apply_terrain_blobs,
                     generate_chunk_weathering_and_precipitation,
                     generate_chunk_forrestry,
                     generate_chunk_foliage,
                     generate_chunk_fauna,
-
-                    // === DYNAMIC UNLOAD (disabled — see dynamic_chunk_unloading_system) ===
                 ),
             )
             .add_systems(
@@ -57,18 +54,13 @@ impl Plugin for WorldPlugin {
                 (
                     compute_visibility_of_game_entities
                         .after(crate::entities::item::item_tile_management_system),
-                    (
-                        handle_tile_occlusion_updates,
-                        build_quilted_terrain_sprites,
-                        update_tile_visibility.run_if(
-                            |cwss: Res<tiles::CurrentWorldSpriteState>,
-                             camera_moved: Res<camera::CameraMoved>| {
-                                cwss.state == tiles::TerrainSpriteState::RenderReady
-                                    || camera_moved.0
-                            },
-                        ),
-                    )
-                        .chain(),
+                    tiles::track_benchmark,
+                    tiles::render_bench_report_system,
+                    handle_tile_occlusion_updates,
+                    tiles::spawn_tilemap_chunks,
+                    tiles::on_camera_z_changed,
+                    tiles::update_tilemap_chunk_visibility,
+                    tiles::populate_tilemap_chunk_data,
                 ),
             );
     }