feat: soft entity collision, dead code removal, leaf standability fix

- Add TileOccupancy resource and rebuild_tile_occupancy system to track
  per-tile entity counts for soft collision avoidance
- Add collision_delay to Ambulatory; entities try relative-left step on
  occupied tiles, wait 1 tick, then push through
- Fix leaf canopy standability: leaves are now can_stand_in=true,
  can_stand_on=false (walkable, not standable-on)
- Delete FloorTilePrefab / FixtureTilePrefab / FloorTile / FixtureTile /
  TileState (all fully dead — TileMap + ChunkData are sole truth)
- Delete tile_spawns from TerrainBlob (populated but never consumed)
- Delete leaf ghost entity spawn in forestry (orphaned invisible ECS entity)
- Replace log prefab spawn with inline commands.spawn(Transform, Visibility)
- Add TileMap::remove_fixture for future digging/explosion use
- Skip collision avoidance when current tile has >2 entities (handles spawn
  cluster deadlock)

src/main.rs

@@ -11,6 +11,7 @@ mod camera;
 mod config;
 mod constants;
 mod cursor;
+mod debug;
 mod entities;
 mod game;
 mod system_info;
@@ -67,5 +68,6 @@ fn main() {
             Update,
             item_tile_management_system.after(initialize_item_rotation_state),
         )
+        .add_systems(Update, debug::entity_dump::dump_entity_positions)
         .run();
 }