Story 4.2: Implement full AV replacement with WebRTC stream access

- Update FoundryAdapter to properly detect and expose WebRTC stream access
- Modify ScryingPoolStrip to create video elements with WebRTC streams
- Add video container to roster-strip.hbs template with conditional rendering
- Add CSS to hide Foundry's AV dock (#av and .camera-view)
- Add CSS styling for video containers and elements
- Fix unused variable in FoundryAdapter.buildWebRTCSurface
- Add comprehensive test script for stream access implementation

Architecture: Full replacement mode where module hides Foundry's AV dock
and creates its own video elements using game.webrtc.client.getMediaStreamForUser()

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

src/ui/gm/ScryingPoolStrip.js

@@ -28,9 +28,10 @@ export function resolveTargetState(currentState) {
  * @param {object} stateStore
  * @param {object} controller
  * @param {object} adapter
+ * @param {boolean} hasStreamAccess - Whether stream access is available for video replacement
  * @returns {Array<object>}
  */
-export function buildParticipantList(userIds, stateStore, controller, adapter) {
+export function buildParticipantList(userIds, stateStore, controller, adapter, hasStreamAccess = false) {
   return userIds.map(userId => {
     const user = adapter.users.get(userId) ?? { name: userId, avatar: null };
     const state = stateStore.getState(userId) ?? 'active';
@@ -42,6 +43,7 @@ export function buildParticipantList(userIds, stateStore, controller, adapter) {
       stateLabel: _stateLabel(state),
       hasPendingOp: controller.hasPendingOp ? controller.hasPendingOp(userId) : false,
       isCurrentUser: adapter.users.current?.()?.id === userId,
+      hasStreamAccess,
     };
   });
 }
@@ -152,11 +154,15 @@ export class ScryingPoolStrip extends _AppBase {
       ? this._adapter.users.all().map(u => u.id)
       : [];
 
+    // Check if we have stream access for video replacement (full AV replacement mode)
+    const hasStreamAccess = this._adapter.webrtc?.getMediaStreamForUser !== undefined;
+
     const participants = buildParticipantList(
       userIds,
       this._stateStore,
       this._controller,
-      this._adapter
+      this._adapter,
+      hasStreamAccess
     );
 
     return {
@@ -164,6 +170,7 @@ export class ScryingPoolStrip extends _AppBase {
       isExpanded: this._isExpanded,
       isEmpty: participants.length === 0,
       showFirstOpenTip,
+      hasStreamAccess,
     };
   }
 
@@ -207,6 +214,11 @@ export class ScryingPoolStrip extends _AppBase {
     if (isFirstOpen) {
       game.user?.setFlag?.('video-view-manager', 'firstStripOpen', true);
     }
+
+    // Attach video streams if we have stream access (full AV replacement mode)
+    if (this._adapter.webrtc?.getMediaStreamForUser !== undefined) {
+      this._attachVideoStreams(el);
+    }
   }
 
   /** @inheritdoc */
@@ -323,6 +335,80 @@ export class ScryingPoolStrip extends _AppBase {
     const baseRevision = this._controller.getRevision?.(participantId) ?? 0;
     this._controller.action('strip', participantId, targetState, opId, baseRevision);
   }
+
+  /**
+   * Attaches video stream elements for all participants in the strip.
+   * Called from activateListeners() when stream access is available.
+   * @param {HTMLElement} container - The container element (html from activateListeners)
+   */
+  _attachVideoStreams(container) {
+    const participantItems = container.querySelectorAll('.sp-strip__participant-item');
+    for (const item of participantItems) {
+      const userId = item.querySelector('[data-user-id]')?.dataset.userId;
+      if (userId) {
+        this._attachVideoStream(userId, item);
+      }
+    }
+  }
+
+  /**
+   * Attaches a video element with the WebRTC stream for a specific user.
+   * Creates a video element with srcObject set to the user's MediaStream.
+   * The video element is appended to the video container within the participant item.
+   * @param {string} userId - The user ID to attach video for
+   * @param {HTMLElement} participantItem - The participant list item element
+   */
+  _attachVideoStream(userId, participantItem) {
+    const stream = this._adapter.webrtc.getMediaStreamForUser(userId);
+    
+    // Check if video container exists
+    const videoContainer = participantItem.querySelector('.sp-participant-video');
+    if (!videoContainer) {
+      console.warn('[ScryingPool] No video container found for user:', userId);
+      return;
+    }
+
+    // Remove any existing video element
+    const existingVideo = videoContainer.querySelector('video');
+    if (existingVideo) {
+      existingVideo.remove();
+    }
+
+    // If no stream available, don't create video element (will show avatar fallback)
+    if (!stream) {
+      return;
+    }
+
+    // Create new video element
+    const videoElement = document.createElement('video');
+    videoElement.srcObject = stream;
+    videoElement.autoplay = true;
+    videoElement.playsInline = true;
+    videoElement.muted = userId === this._adapter.users.current?.()?.id;
+
+    // Add CSS class for styling
+    videoElement.className = 'sp-participant-video__element';
+
+    // Set up error handling
+    videoElement.addEventListener('error', () => {
+      console.warn('[ScryingPool] Video element error for user:', userId);
+    });
+
+    videoContainer.appendChild(videoElement);
+  }
+
+  /**
+   * Refreshes all video streams for participants.
+   * Called when stream state changes (user joins/leaves, mute/unmute).
+   */
+  _refreshVideoStreams() {
+    if (!this._adapter.webrtc?.getMediaStreamForUser) {
+      return;
+    }
+    
+    // Re-render to ensure DOM is up to date
+    this.render(false);
+  }
 }
 
 /**