ui: Filesystem @mentions for Chat Form (#26715)

* base : @-mention picker foundation - glob search, picker nav, highlight

* feat : @-mention file/folder picker and mention badges in message bubbles

* fix: Imports

* feat : wire the @-mention picker into the chat form

* fix: Bound the glob-search result cache key and prune stale entries

tools/ui/src/lib/enums/index.ts

@@ -24,7 +24,8 @@ export {
 	MessageRole,
 	MessageType,
 	PdfViewMode,
-	ReasoningFormat
+	ReasoningFormat,
+	FileMentionEntryType
 } from './chat.enums';
 
 export { SessionRecordType } from './conversation-import.enums';