Freeze mixed-file retrieval diagnostic and shared-engine evaluator

fixtures/mixed/sources/apps__desktop__src__selection-state.ts

@@ -0,0 +1,24 @@
+/** Preserve the user's result choice while progressive indexing hides it briefly. */
+export class ResultSelection {
+  private scope: string | null = null;
+  private intendedPath: string | null = null;
+
+  begin(scope: string) {
+    if (scope !== this.scope) {
+      this.scope = scope;
+      this.intendedPath = null;
+    }
+  }
+
+  choose(path: string) {
+    this.intendedPath = path;
+  }
+
+  resolve(paths: readonly string[]): number {
+    if (!paths.length) return -1;
+    if (this.intendedPath === null) this.intendedPath = paths[0];
+    const intended = paths.indexOf(this.intendedPath);
+    // A temporary fallback is presentation, not a new user choice.
+    return intended >= 0 ? intended : 0;
+  }
+}