Add headless wgpu vision and camera controls

docs/grid-agent-architecture.md

@@ -119,9 +119,15 @@ avatar session -> persistent Mentra agent -> Responses SSE / compaction / memory
                                |                   |
                                |                   +-> AuthorizedToolBackend
                                +-> one-shot Mentra safety reviewer when required
+
+scene snapshot -> cached headless wgpu color/depth render -> JPEG -> Mentra image
+                      `-> deterministic software fallback
 ```
 
-The package has no build script or direct native dependency. The focused
+The package has no build script. Its cross-platform `wgpu` path uses the
+platform graphics backend selected by wgpu and requires no window or display;
+the software fallback remains available when adapter creation or rendering
+fails. The focused
 `dependency_policy` test rejects subprocess launch sites, unsafe/native ABI
 source, build scripts, and unreviewed direct dependency names in this package.
 The precise LLM compatibility and cancellation contract is documented in