test(download): retry media-download Windows tests to absorb runner cold-start variance (#1708)

* test(download): retry media-download Windows tests to absorb runner cold-start variance

src/download/media-download.test.ts > 'keeps custom filenames inside the
output directory' timed out at the default 5000ms on CI run 26217100578
(Windows shard 2/2). The other two cases in the same describe block
completed in ~400ms, so the failure is cold-start cost of the first
http.createServer + downloadMedia roundtrip on a loaded GitHub Actions
Windows runner, not a logic regression.

Adopt the same { retry: process.platform === 'win32' ? 2 : 0 } describe
option that src/download/index.test.ts already uses for the same class
of Windows-only network/IO flake.

* test(download): trim media-download retry comment to match sibling tone

src/download/index.test.ts uses a 2-line comment for the same pattern.
The CI run id + redundant cross-reference belong in commit history, not
inline.

Author: Benjamin-eecs

src/download/media-download.test.ts

@@ -31,7 +31,9 @@ async function startServer(handler: http.RequestListener): Promise<string> {
   return `http://127.0.0.1:${address.port}`;
 }
 
-describe('media downloads', () => {
+// Windows runners occasionally exceed the default 5s timeout on the first
+// http.createServer + downloadMedia roundtrip (cold-start cost on a loaded VM).
+describe('media downloads', { retry: process.platform === 'win32' ? 2 : 0 }, () => {
   it('keeps custom filenames inside the output directory', async () => {
     const baseUrl = await startServer((_req, res) => {
       res.statusCode = 200;