feat: add ephemeral webcam faces and adaptive screens

BUILD_PLAN.md

@@ -120,6 +120,12 @@ rejected; selected cell concurrency passes a repeatable load test.
 
 ## M5 — profile and webcam faces
 
+Status: **implemented and integrated**. Signed-in members can start an optional
+camera face only from the Character dialog; a persistent live indicator and
+one-click Stop remain visible while active. Capture is tab-ephemeral, audio-free,
+never recorded or uploaded, follows the humanoid across scene transitions, and
+is torn down on Stop, track end, revocation, or page exit.
+
 - Generated profile face is the default.
 - Webcam face is opt-in and ephemeral: explicit contextual permission, active
   indicator, one-click stop, no recording/storage by default.
@@ -131,9 +137,17 @@ cannot subscribe; the full product works without a camera.
 
 ## M6 — office media surfaces
 
+Status: **implemented and integrated for peer-to-peer hosted sharing**. Authored
+Three.js monitors remain dark until an authorized viewer explicitly opts in;
+presenters choose a tab/window through the browser prompt and have an immediate
+kill switch. Signaling grants, TURN grants, video textures, late join, reconnect,
+and revoke lifecycle are bounded and tested. Presenter encoding defaults to
+1280×720 at 15 fps and 1.5 Mbps with capability-safe browser fallback.
+
 - `MediaSurface` records identify office/room/screen, ACL, source, and state.
-- WebRTC SFU track after authorization and explicit viewer opt-in; Three.js gets
-  a video texture only while subscribed.
+- WebRTC peer track after authorization and explicit viewer opt-in; Three.js
+  gets a video texture only while subscribed. An SFU is a later scale-out
+  option, not a core requirement for the bounded eight-participant room.
 - Share tab/window by default, muted viewer autoplay, visible broadcast state,
   presenter kill switch, late join and reconnect.