feat(core): open doc in semantic and keyword result (#13217)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Added clickable document titles in AI chat search results, allowing
users to open documents directly from chat interactions.
* Enhanced interactivity in AI chat by making relevant search result
titles visually indicate clickability (pointer cursor).

* **Style**
* Updated styles to visually highlight clickable search result titles in
AI chat results.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/core/src/desktop/pages/workspace/chat/index.tsx

@@ -94,6 +94,7 @@ export const Component = () => {
   const chatToolContainerRef = useRef<HTMLDivElement>(null);
   const widthSignalRef = useRef<Signal<number>>(signal(0));
   const client = useCopilotClient();
+  const workbench = useService(WorkbenchService).workbench;
 
   const workspaceId = useService(WorkspaceService).workspace.id;
 
@@ -173,6 +174,13 @@ export const Component = () => {
     setStatus(context.status ?? 'idle');
   }, []);
 
+  const onOpenDoc = useCallback(
+    (docId: string) => {
+      workbench.openDoc(docId, { at: 'active' });
+    },
+    [workbench]
+  );
+
   const confirmModal = useConfirmModal();
   const specs = useAISpecs();
   const mockStd = useMockStd();
@@ -208,6 +216,7 @@ export const Component = () => {
       confirmModal.openConfirmModal
     );
     content.createSession = createSession;
+    content.onOpenDoc = onOpenDoc;
 
     if (!chatContent) {
       // initial values that won't change
@@ -232,6 +241,7 @@ export const Component = () => {
     confirmModal,
     onContextChange,
     specs,
+    onOpenDoc,
   ]);
 
   // init or update header ai-chat-toolbar