feat(simulation): add tile-type layer, content loader, and chunk streaming

Spatial chain for Sprint 23 (#576, #577, #578):

- TileKind enum (Floor/Wall/Void/Restricted) on WalkabilityMap with
  set_tile_kind/tile_kind API, backward-compatible with existing
  is_walkable/set_walkable
- Location YAML tile format: tiles as string arrays (F/W/V/R chars),
  load_location_tiles() stamps tile data onto WalkabilityMap from
  ContentStore on production startup
- Chunk streaming system: ChunkLoadRadius + ChunkStreamingCadence
  resources, loads/unloads chunks around player position on cadence.
  v0.1 radius covers full district (no streaming stutter)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/simulation/mod.rs

@@ -4,6 +4,7 @@
 use bevy_app::prelude::*;
 use bevy_ecs::schedule::IntoScheduleConfigs;
 
+pub mod chunk_streaming;
 pub mod contraband;
 pub mod conversation;
 pub mod dialogue;
@@ -50,6 +51,8 @@ impl Plugin for SimulationPlugin {
             .init_resource::<crate::knowledge::EntityRegistry>()
             .init_resource::<sound::SoundEventQueue>()
             .init_resource::<spatial::NaiveSpatialIndex>()
+            .init_resource::<chunk_streaming::ChunkLoadRadius>()
+            .init_resource::<chunk_streaming::ChunkStreamingCadence>()
             .init_resource::<follow::FollowEndEventQueue>()
             .init_resource::<monologue::PostConversationQueue>()
             .init_resource::<poi_discovery::PoiDiscoveryEventQueue>()
@@ -127,6 +130,12 @@ impl Plugin for SimulationPlugin {
             .add_systems(
                 Update,
                 zone::detect_zone_crossings.after(movement::validate_movement),
+            )
+            // Chunk streaming (#578, D-012) — loads/unloads chunks around the player.
+            // Runs before input processing so chunks are available for the current tick.
+            .add_systems(
+                Update,
+                chunk_streaming::chunk_streaming.before(input::process_player_input),
             );
 
         tracing::debug!("SimulationPlugin initialized");