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/constants/index.ts

@@ -39,6 +39,7 @@ export * from './max-bundle-size';
 export * from './mcp';
 export * from './mcp-form';
 export * from './mcp-resource';
+export * from './mention-badge';
 export * from './message-export';
 export * from './path-display';
 export * from './model-id';