test(jassub): [PKG-JASSUB-09] isolate synchronous native bitmap stalls

refactor/risks.json

@@ -5901,9 +5901,11 @@
         "test/browser/jassub-native.spec.js",
         "test/browser/jassub-hybrid.spec.js",
         "refactor/changes/2026-09-15-CI-01-jassub-installed.md",
-        "refactor/baselines/ci-jassub-installed-validation.json"
+        "refactor/baselines/ci-jassub-installed-validation.json",
+        "refactor/changes/2026-09-15-PKG-JASSUB-09-native-call.md",
+        "refactor/baselines/jassub-native-call-validation.json"
       ],
-      "compatibleResolution": "Isolate native media/compositor/readback and sequence effects without globally disabling default offscreen or deleting assertions. The pre-09 artifact also fails in the same sequence; do not claim the new hybrid guard caused or fixed this separate failure.",
+      "compatibleResolution": "Isolate native media/compositor/readback and sequence effects without globally disabling default offscreen or deleting assertions. The pre-09 artifact also fails in the same sequence; do not claim the new hybrid guard caused or fixed this separate failure. Single-flight controls also stall; API-entry/return timing locates a captured delay before createImageBitmap returns its Promise, alongside synchronous main-thread canvas readback. A script-free native host has the same ten-second observation despite an eventual-pixel pass. Retain latency evidence; neither core scripts nor concurrent creation are required for that control stall.",
       "closureCriteria": "Identify and verify a compatible fix or a reviewed precise platform boundary with native controls. Preserve known red sequence and successful standalone comparison; candidate playback/fullscreen pixels and lifetime must be justified, not merely rerun to green."
     },
     {