perf(test): keep single media server and fast cleanup

src/media/server.ts

@@ -63,9 +63,15 @@ export function attachMediaRoutes(
       res.send(data);
       // best-effort single-use cleanup after response ends
       res.on("finish", () => {
-        setTimeout(() => {
-          fs.rm(realPath).catch(() => {});
-        }, 50);
+        const cleanup = () => {
+          void fs.rm(realPath).catch(() => {});
+        };
+        // Tests should not pay for time-based cleanup delays.
+        if (process.env.VITEST || process.env.NODE_ENV === "test") {
+          queueMicrotask(cleanup);
+          return;
+        }
+        setTimeout(cleanup, 50);
       });
     } catch (err) {
       if (err instanceof SafeOpenError) {