Prepare text search during media setup and retain query sessions through promotion

apps/desktop/src/search-state.ts

@@ -17,9 +17,15 @@ export const SEMANTIC_SETTLE_MS = 120;
 /** A rebuild retains the previous committed generation. Backend readiness is
  * withdrawn only while a replacement query graph is being prepared. */
 export function semanticAvailable(
-  status: { ready: boolean; generation: number | null } | null,
+  status: {
+    ready: boolean;
+    generation: number | null;
+    coverage?: string | null;
+  } | null,
 ) {
-  return Boolean(status?.ready && status.generation !== null);
+  return Boolean(
+    status?.ready && status.generation !== null && status.coverage !== null,
+  );
 }
 
 /** One active request per lane; intermediate keystrokes collapse to the latest.