feat: 相册下载胶囊自适应尺寸(随图块大小缩放)

- AttachmentDownloadPill 新增 adaptive 模式:用容器查询单位 cqw + clamp,
  尺寸随所在容器宽度缩放(图标框 22~30px、图标 13~18px、文字 10~12px)
- 相册图块设 container-type: inline-size 作为查询容器,小缩略图上的下载按钮
  自动缩小;单图/视频默认固定尺寸不受影响

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/messageStream/bubbles/AlbumBubble.tsx

@@ -51,6 +51,8 @@ export function AlbumBubble({ post }: { post: Post }) {
                 top: `${tile.top * 100}%`,
                 width: `calc(${tile.width * 100}% - ${ALBUM_GAP}px)`,
                 height: `calc(${tile.height * 100}% - ${ALBUM_GAP}px)`,
+                // Query container so the download pill scales with this tile.
+                containerType: "inline-size",
               }}
             >
               <button
@@ -76,7 +78,11 @@ export function AlbumBubble({ post }: { post: Post }) {
                 ) : null}
               </button>
               {!isLastSlot ? (
-                <AttachmentDownloadPill postId={post.id} attachment={att} />
+                <AttachmentDownloadPill
+                  postId={post.id}
+                  attachment={att}
+                  adaptive
+                />
               ) : null}
             </div>
           );