fix(room): revert stale edited_at if messageGet fetch fails

onMessageEdited optimistically set edited_at, then fetched the full
message. If the fetch failed the "Edited" indicator persisted even though
the content was stale. Fix by capturing the original edited_at and
reverting it in the catch block — consistent with editMessage rollback.

src/contexts/room-context.tsx

@@ -500,13 +500,16 @@ export function RoomProvider({
           const client = wsClientRef.current;
           if (!client) return;
 
-          // Optimistic update: set edited_at immediately
+          // Capture original edited_at for rollback if fetch fails
+          let rollbackEditedAt: string | null = null;
           setMessages((prev) => {
+            const msg = prev.find((m) => m.id === payload.message_id);
+            rollbackEditedAt = msg?.edited_at ?? null;
             const updated = prev.map((m) =>
               m.id === payload.message_id ? { ...m, edited_at: payload.edited_at } : m,
             );
-            const msg = updated.find((m) => m.id === payload.message_id);
+            const saved = updated.find((m) => m.id === payload.message_id);
-            if (msg) saveMessage(msg).catch(() => {});
+            if (saved) saveMessage(saved).catch(() => {});
             return updated;
           });
 
@@ -526,12 +529,19 @@ export function RoomProvider({
                   : m,
               );
               // Persist to IndexedDB
-              const msg = merged.find((m) => m.id === payload.message_id);
+              const saved = merged.find((m) => m.id === payload.message_id);
-              if (msg) saveMessage(msg).catch(() => {});
+              if (saved) saveMessage(saved).catch(() => {});
               return merged;
             });
           } catch {
-            // Silently ignore - the optimistic update already applied
+            // Revert edited_at if the fetch failed
+            if (rollbackEditedAt !== null) {
+              setMessages((prev) =>
+                prev.map((m) =>
+                  m.id === payload.message_id ? { ...m, edited_at: rollbackEditedAt! } : m,
+                ),
+              );
+            }
           }
         },
         onMessageRevoked: async (payload) => {