fix(room): fix Enter-on-category via React state update instead of DOM manipulation

Problem: dispatchEvent('input') doesn't trigger React's onChange in React 17+.

Solution: pass onCategoryEnter callback from ChatInputArea to MentionPopover.
When Enter is pressed on a category, MentionPopover calls onCategoryEnter(category)
which directly calls React setState (onDraftChange, setCursorPosition,
setShowMentionPopover) inside ChatInputArea, properly triggering re-render.

src/components/room/MentionPopover.tsx

@@ -62,6 +62,8 @@ interface MentionPopoverProps {
   onSelect: (newValue: string, newCursorPosition: number) => void;
   textareaRef: React.RefObject<HTMLTextAreaElement | null>;
   onOpenChange: (open: boolean) => void;
+  /** Called when Enter is pressed on a category — ChatInputArea handles the state update */
+  onCategoryEnter: (category: string) => void;
 }
 
 // Category configuration with icons and colors
@@ -373,6 +375,7 @@ export function MentionPopover({
   onSelect,
   textareaRef,
   onOpenChange,
+  onCategoryEnter,
 }: MentionPopoverProps) {
   const [position, setPosition] = useState<PopoverPosition>({ top: 0, left: 0 });
   const [selectedIndex, setSelectedIndex] = useState(0);
@@ -385,6 +388,8 @@ export function MentionPopover({
   const selectedIndexRef = useRef(selectedIndex);
   const handleSelectRef = useRef<(s: MentionSuggestion) => void>(() => {});
   const closePopoverRef = useRef<() => void>(() => {});
+  const onCategoryEnterRef = useRef(onCategoryEnter);
+  onCategoryEnterRef.current = onCategoryEnter;
 
   // Parse mention state
   const mentionState = useMemo<MentionState | null>(() => {
@@ -632,23 +637,9 @@ export function MentionPopover({
         if (!item) return;
 
         if (item.type === 'category') {
-          // Enter a category: append ':' to textarea to trigger next-level list
+          // Enter a category: let ChatInputArea handle the state update
           e.preventDefault();
-          const category = item.category;
-          const textarea = textareaRef.current;
-          if (!textarea) return;
-          const curPos = textarea.selectionStart;
-          const val = textarea.value;
-          // Replace @xxx with @xxx: to enter the category
-          const textBefore = val.substring(0, ms.startPos);
-          const afterPartial = val.substring(ms.startPos + ms.category.length + 1); // skip '@' + category
-          const newVal = textBefore + '@' + category + ':' + afterPartial;
-          const newPos = ms.startPos + 1 + category.length + 1; // after '@ai:'
-          textarea.value = newVal;
-          textarea.setSelectionRange(newPos, newPos);
-          textarea.focus();
-          // Dispatch input event so React picks up the change
-          textarea.dispatchEvent(new Event('input', { bubbles: true }));
+          onCategoryEnterRef.current(item.category!);
         } else if (item.type === 'item') {
           // Insert the mention
           e.preventDefault();

src/components/room/RoomChatPanel.tsx

@@ -35,6 +35,8 @@ const MENTION_POPOVER_KEYS = ['Enter', 'Tab', 'ArrowUp', 'ArrowDown'];
 
 export interface ChatInputAreaHandle {
   insertMention: (id: string, label: string, type: 'user' | 'ai') => void;
+  /** Insert a category prefix (e.g. 'ai') into the textarea and trigger React onChange */
+  insertCategory: (category: string) => void;
 }
 
 interface ChatInputAreaProps {
@@ -131,6 +133,26 @@ const ChatInputArea = memo(function ChatInputArea({
         }
       }, 0);
     },
+    insertCategory: (category: string) => {
+      // Enter a category: e.g. @ai → @ai:
+      if (!textareaRef.current) return;
+      const textarea = textareaRef.current;
+      const textBefore = textarea.value.substring(0, textarea.selectionStart);
+      const atMatch = textBefore.match(MENTION_PATTERN);
+      if (!atMatch) return;
+      const [fullMatch] = atMatch;
+      const startPos = textarea.selectionStart - fullMatch.length;
+      const before = textarea.value.substring(0, startPos);
+      const afterPartial = textarea.value.substring(startPos + fullMatch.length);
+      const newValue = before + '@' + category + ':' + afterPartial;
+      const newCursorPos = startPos + 1 + category.length + 1; // after '@ai:'
+      // Directly update React state to trigger mention detection
+      onDraftChange(newValue);
+      setCursorPosition(newCursorPos);
+      const textBefore2 = newValue.substring(0, newCursorPos);
+      const match = textBefore2.match(MENTION_PATTERN);
+      setShowMentionPopover(!!match);
+    },
   }));
 
   const handleChange = (e: React.ChangeEvent<HTMLTextAreaElement>) => {
@@ -261,7 +283,24 @@ const ChatInputArea = memo(function ChatInputArea({
           onSelect={handleMentionSelect}
           textareaRef={textareaRef}
           onOpenChange={setShowMentionPopover}
-          onMentionConfirm={handleMentionSelect}
+          onCategoryEnter={(category: string) => {
+            // Enter a category: @ai → @ai: to show next-level items
+            if (!textareaRef.current) return;
+            const textarea = textareaRef.current;
+            const textBefore = textarea.value.substring(0, textarea.selectionStart);
+            const atMatch = textBefore.match(MENTION_PATTERN);
+            if (!atMatch) return;
+            const [fullMatch] = atMatch;
+            const startPos = textarea.selectionStart - fullMatch.length;
+            const before = textarea.value.substring(0, startPos);
+            const afterPartial = textarea.value.substring(startPos + fullMatch.length);
+            const newValue = before + '@' + category + ':' + afterPartial;
+            const newCursorPos = startPos + 1 + category.length + 1;
+            onDraftChange(newValue);
+            setCursorPosition(newCursorPos);
+            const match2 = newValue.substring(0, newCursorPos).match(MENTION_PATTERN);
+            setShowMentionPopover(!!match2);
+          }}
         />
       )}
     </div>