feat: STT transcripts, model catalog+fuzzy resolve, UI audio player & auto-refresh

Core:
- ModelCatalog: periodic background sync of provider models + fuzzy resolve.
  Misspelled model ids map to the nearest match (cheapest on ties); no match
  raises ModelResolutionError with cheapest-first suggestions for the agent.

mcp-server:
- nexus_stt now writes the transcript to a Markdown file in the media dir so it
  appears in the gallery and is readable in the modal.
- media handler resolves model via catalog before generating; returns a note
  when substituting, or a BAD_REQUEST with available models when nothing fits.
- context wires a ModelCatalog per media provider with auto-sync.

admin:
- /media serves correct Content-Type (incl. text/markdown for transcripts).
- Gallery: audio play button on cards, dedicated audio player in modal,
  text/transcript tiles that fetch and render the .md in the modal.
- Header: auto-refresh toggle (5/10/30s) that refreshes the active tab
  without a full page reload; pauses while a modal is open.

NexusAI/packages/mcp-server/src/context.ts

@@ -3,6 +3,7 @@ import {
   KeyCipher,
   KeyResolver,
   MediaStorage,
+  ModelCatalog,
   ProviderRegistry,
   ProvidersStore,
   createNordRouterProviders,
@@ -20,6 +21,8 @@ export interface AppContext {
   storage: MediaStorage;
   journal: Journal;
   providersStore: ProvidersStore;
+  /** Model catalogs keyed by provider name (for sync + fuzzy resolution). */
+  catalogs: Map<string, ModelCatalog>;
   /** Effective default provider name after resolving DB/env. */
   defaultProvider: string;
 }
@@ -47,6 +50,7 @@ export function buildContext(): AppContext {
 
   const resolved = resolver.resolveAll(BUILTINS);
   const defaultProvider = resolver.resolveDefault(resolved);
+  const catalogs = new Map<string, ModelCatalog>();
 
   for (const p of resolved) {
     if (!p.enabled) {
@@ -69,6 +73,12 @@ export function buildContext(): AppContext {
         Object.defineProperty(nr.search, 'name', { value: p.name });
         registry.registerMedia(nr.media);
         registry.registerSearch(nr.search);
+        // Model catalog with periodic background sync + fuzzy resolution.
+        if (p.apiKey) {
+          const catalog = new ModelCatalog(nr.media);
+          catalog.startAutoSync();
+          catalogs.set(p.name, catalog);
+        }
         log.info(`registered provider "${p.name}" (media + search, key: ${p.keySource})`);
       } catch (err) {
         log.warn(`failed to register "${p.name}"`, err instanceof Error ? err.message : String(err));
@@ -82,5 +92,5 @@ export function buildContext(): AppContext {
   log.info('registered local STT provider');
   log.info(`default provider: ${defaultProvider}`);
 
-  return { config, registry, storage, journal, providersStore, defaultProvider };
+  return { config, registry, storage, journal, providersStore, catalogs, defaultProvider };
 }