fix(web): prevent image thumbnails from warping during repaints (#26308)

Author: Yash-Singh1

apps/web/src/components/chat/GuestMessageAttachments.tsx

@@ -43,13 +43,14 @@ export function GuestMessageAttachments(props: {
                     aria-label={`Preview ${image.name}`}
                     onClick={() => props.onOpenImage(image)}
                   >
+                    {/* Isolate the thumbnail raster from nearby activity repaints in Chromium. */}
                     <AttachmentImage
                       name={image.name}
                       mimeType={image.mimeType}
                       src={src}
                       alt={image.name}
                       decoding="async"
-                      className="block size-full object-cover"
+                      className="block size-full transform-gpu object-cover"
                     />
                   </button>
                 ) : (

apps/web/src/components/chat/TimelineUserMessageRow.tsx

@@ -524,14 +524,15 @@ function UserTimelineRow({ row }: { row: Extract<TimelineRow, { kind: "message"
                           ctx.onImageExpand(preview);
                         }}
                       >
+                        {/* Isolate the thumbnail raster from nearby activity repaints in Chromium. */}
                         <AttachmentImage
                           name={image.name}
                           mimeType={image.mimeType}
                           src={image.previewUrl}
                           alt={image.name}
                           decoding="async"
                           loading="lazy"
-                          className="block size-full object-cover"
+                          className="block size-full transform-gpu object-cover"
                         />
                       </button>
                     ) : (