Add headless wgpu vision and camera controls

docs/grid-agent-llm.md

@@ -56,16 +56,22 @@ facility, not a requirement for autonomous operation.
 
 ## Images
 
-Vision captures are real software-rendered viewport images. MetaCrate renders
-the current scene, encodes the final frame directly as JPEG, and attaches it as
-a Mentra image content block. The default 320x180 frame, quality, entity,
-triangle, texture-fetch, decoded-pixel, byte, rate, and concurrency limits are
-validated before runtime. JPEG avoids the much larger PNG payloads.
+Vision captures are reconstructed viewport images rather than screenshots.
+The live service keeps one headless `wgpu` device, renders the current scene to
+an offscreen color/depth target, reads the frame back, encodes it directly as
+JPEG, and attaches it as a Mentra image content block. GPU setup and readback
+run outside the simulator event path. If no compatible adapter is available or
+a frame fails, the same scene is rendered by the deterministic software
+rasterizer. The default 320x180 frame, quality, entity, triangle, texture-fetch,
+decoded-pixel, byte, rate, and concurrency limits are validated before runtime.
+JPEG avoids the much larger PNG payloads.
 
 The current renderer handles legacy prim geometry, approximate texture colors,
-simple avatars, and flat terrain/water. Viewer-grade mesh/sculpt rendering,
-full UV materials, lighting, authoritative terrain, and model-controlled camera
-tools are tracked separately.
+simple avatars, and flat terrain/water. `behavior_camera_set` gives an
+authorized model a bounded position, target, and vertical field of view;
+`behavior_camera_reset` restores the avatar-facing view. Viewer-grade
+mesh/sculpt rendering, full UV materials, lighting, authoritative terrain, and
+avatar/attachment fidelity remain tracked in the renderer issue.
 
 ## Bounds and cancellation