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/world/mod.rs

@@ -2,8 +2,8 @@ use crate::{
     camera,
     config::{GameConfig, VsyncMode},
     world::generation::{
-        generate_chunk_fauna, generate_chunk_foliage, generate_chunk_forrestry,
-        generate_chunk_weathering_and_precipitation, apply_terrain_blobs, spawn_terrain_tasks,
+        apply_terrain_blobs, generate_chunk_fauna, generate_chunk_foliage,
+        generate_chunk_forrestry, generate_chunk_weathering_and_precipitation, spawn_terrain_tasks,
         TerrainBlobStorage,
     },
 };
@@ -16,12 +16,9 @@ pub mod tiles;
 
 pub use chunks::management::*;
 pub use textures::management::*;
-pub use tiles::{prefabs::*, rendering::*, visibility::*};
+pub use tiles::{rendering::*, visibility::*};
 
-pub fn apply_vsync_setting(
-    config: Res<GameConfig>,
-    mut windows: Query<&mut Window>,
-) {
+pub fn apply_vsync_setting(config: Res<GameConfig>, mut windows: Query<&mut Window>) {
     if config.is_changed() {
         if let Ok(mut window) = windows.single_mut() {
             window.present_mode = match config.display.vsync {