test(e2e): stop requiring Content-Length on streamed Route Handler downloads

Next.js 16.4.5 strips Content-Length and Content-Encoding from every
Route Handler response (GHSA-pc58-hwjq-p385); upstream kept that in
16.4.6 and closed the scoped alternative, so a large download now
arrives chunked without a declared length. The history suite still
proves incremental delivery, the full byte count and the content hash,
and checks a declared length whenever one is present.

Author: waleedlatif1

apps/sim/scripts/test-project-file-history-e2e.ts

@@ -69,7 +69,9 @@ async function verifyStreamedDownload(
     signal: AbortSignal.timeout(90_000),
   })
   assert.equal(response.status, 200)
-  assert.equal(Number(response.headers.get('content-length')), expectedBytes)
+  // Next 16.4.5+ strips Content-Length from every Route Handler response (GHSA-pc58-hwjq-p385).
+  const declaredLength = response.headers.get('content-length')
+  if (declaredLength !== null) assert.equal(Number(declaredLength), expectedBytes)
   assert.ok(response.body)
   const reader = response.body.getReader()
   const hash = createHash('sha256')