feat: pass current photo focus to comment sheet in timeline

src/components/pages/grain-timeline.js

···
     _cursor: { state: true },
     _error: { state: true },
     _commentSheetOpen: { state: true },
-    _commentGalleryUri: { state: true }
+    _commentGalleryUri: { state: true },
+    _focusPhotoUri: { state: true },
+    _focusPhotoUrl: { state: true }
   };
 
   static styles = css`
···
     this._error = null;
     this._commentSheetOpen = false;
     this._commentGalleryUri = '';
+    this._focusPhotoUri = null;
+    this._focusPhotoUrl = null;
 
     // Check cache synchronously to avoid flash
     this.#initFromCache();
···
   }
 
   #handleCommentClick(e) {
-    const galleryUri = e.target.closest('grain-gallery-card')?.gallery?.uri;
+    const card = e.target.closest('grain-gallery-card');
+    const galleryUri = card?.gallery?.uri;
     if (!galleryUri) return;
 
     if (!auth.isAuthenticated) {
···
       return;
     }
 
+    // Get current photo from carousel inside the card
+    const carousel = card.shadowRoot?.querySelector('grain-image-carousel');
+    const currentPhoto = carousel?.getCurrentPhoto();
+
     this._commentGalleryUri = galleryUri;
+    this._focusPhotoUri = currentPhoto?.uri || null;
+    this._focusPhotoUrl = currentPhoto?.url || null;
     this._commentSheetOpen = true;
   }
 
   #handleCommentSheetClose() {
     this._commentSheetOpen = false;
     this._commentGalleryUri = '';
+    this._focusPhotoUri = null;
+    this._focusPhotoUrl = null;
   }
 
   render() {
···
         <grain-comment-sheet
           ?open=${this._commentSheetOpen}
           galleryUri=${this._commentGalleryUri}
+          focusPhotoUri=${this._focusPhotoUri || ''}
+          focusPhotoUrl=${this._focusPhotoUrl || ''}
           @close=${this.#handleCommentSheetClose}
         ></grain-comment-sheet>
       </grain-feed-layout>