Fix OA workspace cover thumbnails and add space chat new session.

Resolve mindspace-cover images from workspace directories when generating feed thumbnails, refresh stale SVGs missing embedded photos, and disable thumbnail API caching so fixes take effect immediately. Also add a new session control to the space chat panel, including on mobile.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/hooks/usePageEditSubChat.ts

@@ -306,6 +306,12 @@ export function usePageEditSubChat({
     }
   }, [connectSubSession, start]);
 
+  const newSession = useCallback(async () => {
+    if (chatState === 'streaming' || chatState === 'loading' || chatState === 'connecting') return;
+    await close({ merge: false });
+    await start();
+  }, [chatState, close, start]);
+
   const startedRef = useRef(false);
 
   useEffect(() => {
@@ -335,6 +341,7 @@ export function usePageEditSubChat({
     dismissNotice,
     retryConnect,
     openRecharge: () => setNotice('余额不足，请充值后继续使用'),
+    newSession,
     close,
   };
 }