fix(M03): make WMO build queue cold-load safe

docs/modules/wmo-render-build-queue.md

@@ -69,7 +69,11 @@ editor UI are forbidden dependencies.
 | `has_pending()` / `pending_count()` | Query | Observe FIFO entries including duplicate/stale keys | Renderer main thread | None |
 | `active_job_count()` | Query | Count current keyed jobs | Renderer main thread | None |
 | `front_key()` / `pop_front()` | Queue operation | Inspect/remove one front FIFO key | Renderer main thread | Empty queue returns empty String |
-| `job_for(placement_key)` | Query | Borrow current typed job or null for stale key | Renderer main thread | No ownership transfer |
+| `has_job(placement_key)` | Query | Distinguish a live job from a stale FIFO key | Renderer main thread | Unknown key returns false |
+| `job_for(placement_key)` | Diagnostic/test query | Borrow current job through its `RefCounted` base or return null | Renderer main thread | Runtime loader uses typed accessors instead |
+| `root_for` / `render_resource_for` | Typed query | Borrow current engine references without exposing job implementation type | Renderer main thread | Stale key returns null |
+| `mesh_index_for` / `multimesh_index_for` | Typed query | Return current cursors | Renderer main thread | Stale key returns zero |
+| `adopt_cursors(placement_key, next_mesh_index, next_multimesh_index)` | Command/query | Atomically update current job cursors | Renderer main thread | Stale key returns false |
 | `cancel(placement_key)` | Command/query | Remove keyed job and first matching FIFO key | Renderer main thread | Unknown key returns false; stale duplicates remain |
 | `clear()` | Command | Release all job/key references idempotently | Reset/shutdown | Does not free engine objects |
 | `diagnostic_snapshot()` | Query | Return detached FIFO order and key-sorted scalar jobs | Caller-owned result | None |
@@ -134,15 +138,15 @@ sequenceDiagram
     participant Planner as WmoRenderBuildStepPlanner
     Loader->>Queue: enqueue(key, root, resource)
     loop while permit and pending key
-        Loader->>Queue: front_key + job_for
+        Loader->>Queue: front_key + has_job
         alt stale key
             Loader->>Queue: pop_front
         else live job
-            Queue-->>Loader: borrowed Job
+            Loader->>Queue: typed root/resource/cursor accessors
             Loader->>Planner: plan_step(counts, job cursors)
             Planner-->>Loader: operation and next cursors
             Loader->>Loader: materialize one group on main thread
-            Loader->>Job: adopt_cursors(next mesh, next MultiMesh)
+            Loader->>Queue: adopt_cursors(key, next mesh, next MultiMesh)
             Loader->>Loader: consume one permit
         end
     end