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/utils/index.ts

@@ -174,13 +174,47 @@ export {
 export {
 	splitPathQuery,
 	buildCaseInsensitiveGlob,
+	buildGlobSearchArgs,
 	rankEntries,
 	joinPath,
 	highlightMatch,
 	type GlobEntry,
+	type GlobSearchArgs,
 	type PathQuery
 } from './working-directory';
 
+// Shared `file_glob_search` runner with a short-lived result cache
+export {
+	runGlobSearch,
+	runGlobSearchWithChildren,
+	type GlobEntryResult,
+	type GlobSearchResult
+} from './glob-search';
+
+// Mention-token detection (for the `@`-triggered file/folder mention picker)
+export {
+	findMentionToken,
+	takeMentionDismissSnapshot,
+	type MentionDismissSnapshot
+} from './mention-token';
+
+// Mention-chip visual contract shared by the rehype file-badge plugin,
+// plus the `[name](file://...)` link helpers the mention picker splices in
+export {
+	fileMentionLinkRe,
+	encodeFileLinkPath,
+	decodeFileLinkPath,
+	MENTION_BADGE_CLASSNAME,
+	MENTION_BADGE_ICON_CLASSNAME,
+	MENTION_BADGE_SVG_ATTRIBUTES,
+	MENTION_BADGE_FILE_ICON_PATHS,
+	MENTION_BADGE_FOLDER_ICON_PATHS,
+	getMentionBadgeIconPaths,
+	getMentionBadgeLabel,
+	buildMentionInsertion,
+	mentionLinkEndingAt
+} from './mention-badge';
+
 // Agentic content utilities (structured section derivation)
 export {
 	deriveAgenticSections,