render: extract static M2 build resource observer

docs/modules/world-renderer.md

@@ -142,6 +142,7 @@ from externally reading/writing loader-private queue, task, cache and tile-state
 | `M2BuildBatchPlanner.plan_batch` | Internal pure M2 service | Selects static/animated batch count and next group cursor | Main/any thread; stateless | Non-positive selected limit clamps to one; empty range completes |
 | `M2BuildDispatchPlanner.plan_step` | Internal pure M2 service | Selects wait, animated/static materialization or no-Node advancement from observed resource state | Main/any thread; stateless | Pending animation has priority; unresolved static Mesh waits |
 | `M2BuildResourceSnapshot` | Internal M2 value contract | Carries per-step normalized path, animated/static references and pending/missing observations | Renderer main thread; one build operation | Values retained exactly; release never frees resources |
+| `M2StaticBuildResourceObserver.observe` | Internal M2 I/O service | Produces cached/pending/requested/missing static snapshot phase | Renderer main thread; stateless | Invalid composition rejected; no candidate marks missing |
 | `M2BuildQueue` / `M2BuildJob` | Internal M2 pending-state service | Own typed root/groups/cursor jobs and FIFO/stale tile keys | Renderer main thread; map session | Invalid enqueue rejected; stale keys drain independently of jobs |
 | `M2StaticBatchMaterializer.materialize_batch` | Internal M2 scene-materialization service | Builds and attaches one prepared-Mesh MultiMesh transform slice | Renderer main thread; stateless after each call | Invalid/empty input returns null; bounds are caller precondition |
 | `M2RuntimeMeshRebuildClassifier` | Internal memoized M2 service | Detects billboard/UV-rotation metadata requiring stale cached-mesh rebuild | Renderer main thread; cached until reset | Invalid variants/indices skipped; first path decision wins |
@@ -393,9 +394,10 @@ sequenceDiagram
   without controlling engine lifetime.
   `M2BuildQueue` owns typed pending jobs, FIFO/stale keys, grouped-transform
   references and group/offset/serial cursors without freeing engine objects.
-  `M2StaticBatchMaterializer` owns static MultiMesh construction/attachment;
-  the loader retains resource observation/requests, action execution,
-  cursor adoption, root cleanup, budgets and Editor ownership.
+  `M2StaticBuildResourceObserver` owns static Mesh lookup/request admission and
+  snapshot adoption. `M2StaticBatchMaterializer` owns static MultiMesh
+  construction/attachment; the loader retains animated observation/requests,
+  action execution, cursor adoption, root cleanup, budgets and Editor ownership.
 - `WmoPlacementResolver` is stateless and owns only call-local cache-key,
   identity and transform values. `WmoPlacementRegistry` owns only placement-key
   reference sets. `WmoRenderBuildStepPlanner` owns only a call-local operation
@@ -416,15 +418,17 @@ sequenceDiagram
   for billboard/UV-rotation material refresh and is composed by the runtime Mesh
   finalizer. The raw repository loads value data; loader retains Mesh adoption.
 - `M2MeshLoadPipelineState` owns static M2 pending Resource paths, opaque
-  terminal statuses and completion-order finalize FIFO. The loader retains cache
-  path selection, ResourceLoader calls, permits and adoption decisions; prototype
-  cache state owns shared missing outcomes.
+  terminal statuses and completion-order finalize FIFO. The static observer owns
+  cache path selection, request admission and initial snapshot adoption. The
+  loader retains ResourceLoader polling/finalize, permits and terminal adoption;
+  prototype cache state owns shared missing outcomes.
 - `M2MeshResourceCacheState` owns prepared static Mesh references and releases
   them at the existing final-shutdown site. Prototype state and materialization
   belong to the sibling cache service and loader respectively.
 - `M2MeshResourceExtractor` owns depth-first first-Mesh selection and temporary
-  PackedScene instance destruction. The loader retains ResourceLoader I/O,
-  cache/missing adoption and materialization.
+  PackedScene instance destruction. The static observer admits ResourceLoader
+  requests and initial cache/missing adoption; the loader retains polling,
+  terminal adoption and materialization.
 - `M2RuntimeMeshFinalizer` owns refresh version `2`, classifier lifetime,
   M2Builder rebuild and original-Mesh fallback. The loader loads raw data only
   after the finalizer reports that a cached Mesh is stale.
@@ -579,6 +583,7 @@ Exact exported settings and cache versions remain documented in [`../../RENDER.m
 | M2 build batch planner | Implemented extraction | Scene-free limit/count/cursor/source/timing contract | Spatial cells and asset-backed p95/p99 remain pending |
 | M2 build dispatch planner | Implemented extraction | Scene-free priority/action/transition/source/timing contract | Resource observation/orchestration and asset-backed traversal remain pending |
 | M2 build resource snapshot | Implemented extraction | Typed identity/adoption/lifetime/source/timing contract | Resource observation service and asset-backed traversal remain pending |
+| M2 static build resource observer | Implemented extraction | Cache/pending/path/request/source/timing contract | Asset-backed traversal and finalize extraction pending |
 | M2 build queue | Implemented extraction | Typed lifecycle/FIFO/progress/lifetime/source/timing contract | Resource dispatch and asset-backed traversal remain pending |
 | M2 animation load pipeline state | Implemented extraction | Synthetic lifecycle/FIFO/source/timing contract | Asset-backed traversal/leak/animation-fidelity/p95/p99 pending |
 | M2 animated scene finalizer | Implemented extraction | Synthetic type/lifetime/material/player/source/timing contract | Asset-backed GLB traversal/material/animation comparison pending |
@@ -652,6 +657,7 @@ Exact exported settings and cache versions remain documented in [`../../RENDER.m
 | `src/render/m2/m2_static_batch_materializer.gd` | Static MultiMesh construction, render setup and attachment |
 | `src/render/m2/m2_build_dispatch_planner.gd` | M2 wait/materializer/advance action priority and transition plan |
 | `src/render/m2/m2_build_resource_snapshot.gd` | Typed per-step animated/static observations and borrowed references |
+| `src/render/m2/m2_static_build_resource_observer.gd` | Static Mesh lookup/request/missing snapshot production |
 | `src/render/m2/m2_build_job.gd` | M2 root/groups references and group/offset/serial progress |
 | `src/render/m2/m2_build_queue.gd` | Keyed pending jobs and FIFO/stale tile-key lifecycle |
 | `src/render/m2/m2_mesh_load_pipeline_state.gd` | Static M2 pending Resource paths, terminal statuses and finalize FIFO |
@@ -682,6 +688,7 @@ Exact exported settings and cache versions remain documented in [`../../RENDER.m
 | `src/tools/verify_m2_static_batch_materializer.gd` | Static M2 node/Mesh/render/attachment/boundary/timing regression |
 | `src/tools/verify_m2_build_dispatch_planner.gd` | M2 dispatch priority/action/transition/boundary/timing regression |
 | `src/tools/verify_m2_build_resource_snapshot.gd` | M2 observation identity/adoption/lifetime/boundary/timing regression |
+| `src/tools/verify_m2_static_build_resource_observer.gd` | Static lookup/request/path/boundary/timing regression |
 | `src/tools/verify_m2_build_queue.gd` | M2 job/FIFO/progress/lifetime/boundary/timing regression |
 | `src/tools/verify_m2_mesh_load_pipeline_state.gd` | Static M2 request/terminal/FIFO/boundary/timing regression |
 | `src/tools/verify_m2_mesh_resource_cache_state.gd` | Static M2 Mesh cache ownership/lifetime/boundary/timing regression |