render: extract WMO scene resource finalizer

docs/modules/wmo-scene-resource-cache-state.md

@@ -14,8 +14,9 @@
 
 Own mutually exclusive cached, missing and pending states for normalized WMO
 scene paths. The state accepts only caller-validated `PackedScene` references and
-records `.tscn` paths for threaded requests whose I/O, size limit and cache
-metadata validation remain in `StreamingWorldLoader`.
+records `.tscn` paths for threaded requests. Size admission remains in
+`StreamingWorldLoader`; terminal I/O/probe validation belongs to
+`WmoSceneResourceFinalizer`.
 
 ## Non-goals
 
@@ -33,8 +34,8 @@ flowchart LR
     Loader --> State[WmoSceneResourceCacheState]
     Loader --> Size[File existence and size limit]
     Size --> ResourceLoader[Godot ResourceLoader]
-    ResourceLoader --> Loader
-    Loader --> Probe[Instantiate, metadata/version check, free]
+    ResourceLoader --> Finalizer[WmoSceneResourceFinalizer]
+    Finalizer --> Probe[Instantiate, metadata/version check, free]
     Probe -->|accepted PackedScene or missing| State
     Loader --> Live[Live-prototype fallback]
 ```
@@ -82,7 +83,7 @@ flowchart TD
     Check -->|allowed| Request[Start threaded request]
     Request -->|error| Mark
     Request -->|accepted| Remember[remember_request]
-    Remember --> Poll[Loader polls snapshot]
+    Remember --> Poll[Scene Resource finalizer polls snapshot]
     Poll -->|failure| CompleteMissing[complete as missing]
     Poll -->|loaded| Validate[Instantiate and validate cache metadata]
     Validate -->|valid| CompleteScene[complete with scene]
@@ -114,24 +115,27 @@ stateDiagram-v2
 sequenceDiagram
     participant Loader as StreamingWorldLoader
     participant State as WmoSceneResourceCacheState
+    participant Finalizer as WmoSceneResourceFinalizer
     participant RL as ResourceLoader
     Loader->>State: cached/missing/pending queries
     Loader->>Loader: exists and wmo_max_runtime_scene_mb check
     Loader->>RL: load_threaded_request(.tscn)
     Loader->>State: remember_request(normalized, path)
     loop renderer tick
-        Loader->>State: request_paths_snapshot()
-        Loader->>RL: load_threaded_get_status(path)
+        Loader->>Finalizer: poll_terminal_requests(State)
+        Finalizer->>State: request_paths_snapshot()
+        Finalizer->>RL: load_threaded_get_status(path)
     end
-    Loader->>RL: load_threaded_get(path)
-    Loader->>Loader: instantiate, validate WMO metadata, free probe
-    Loader->>State: complete with scene or as missing
+    Finalizer->>RL: load_threaded_get(path)
+    Finalizer->>Finalizer: instantiate, validate WMO metadata, free probe
+    Finalizer->>State: complete with scene or as missing
 ```
 
 ## Ownership, threading and resources
 
 - State owns three Dictionaries and strong references to accepted PackedScenes.
-- Loader owns paths, file measurement, requests, validation and all Node lifetime.
+- Loader owns paths, file measurement, request admission and placed Nodes;
+  finalizer owns terminal I/O and call-local validation-probe lifetime.
 - All mutation is serialized on the renderer main thread; no mutex is required.
 - Detached request snapshots allow terminal removal while polling.
 - Scene instantiation borrows the PackedScene and does not transfer cache ownership.
@@ -143,7 +147,7 @@ sequenceDiagram
 | Missing `.tscn` | Loader ResourceLoader existence check | Direct missing state | Transient reset permits later retry |
 | Oversize `.tscn` | Loader byte limit | Missing plus unchanged debug log | Raise limit/rebuild, then reset |
 | Request-start/load failure | Loader error/status | Direct or terminal missing | Reset and retry later |
-| Wrong type/stale metadata | Loader PackedScene/probe validation | Terminal missing; probe freed | Rebuild cache and reset |
+| Wrong type/stale metadata | Finalizer PackedScene/probe validation | Terminal missing; probe freed | Rebuild cache and reset |
 | Shutdown while pending | Loader drains snapshot | Clear transient, then full cache release | New loader starts absent |
 
 ## Configuration and capabilities
@@ -184,8 +188,9 @@ in the loader; the state emits no logs.
 | Capability | Status | Evidence | Gap/next step |
 |---|---|---|---|
 | Cached WMO PackedScene state | Implemented extraction | Lifecycle/source/timing and shutdown verifiers | Asset-backed traversal/leak evidence pending |
-| Size and cache metadata validation | Preserved in loader | Source boundary and WMO regressions | Oversize/stale asset fixtures could follow |
-| ResourceLoader I/O and live fallback | Partial/loader-owned | Existing runtime behavior | Separate extraction if justified |
+| Size admission | Preserved in loader | Source boundary and WMO regressions | Oversize asset fixture could follow |
+| Terminal I/O and cache validation | Implemented extraction | Finalizer type/lifetime/source/timing verifier | Serialized stale fixture pending |
+| Live fallback | Loader-owned | Existing runtime behavior | Separate extraction if justified |
 
 ## Known gaps and risks
 
@@ -199,7 +204,8 @@ in the loader; the state emits no logs.
 | Path | Responsibility |
 |---|---|
 | `src/render/wmo/wmo_scene_resource_cache_state.gd` | Scene/missing/request state and resets |
-| `src/scenes/streaming/streaming_world_loader.gd` | Paths, file limit, requests, validation, fallback and Node lifetime |
+| `src/render/wmo/wmo_scene_resource_finalizer.gd` | Terminal I/O, probe validation/lifetime and publication |
+| `src/scenes/streaming/streaming_world_loader.gd` | Paths, file limit, request admission, fallback and placed Nodes |
 | `src/tools/verify_wmo_scene_resource_cache_state.gd` | State, boundary and timing regression |
 | `src/tools/verify_render_runtime_cache_shutdown.gd` | Loader final cache ownership regression |