fix: don't overwrite Phase 2 test video with idle research video

After context.close(), renameLatestWebm would overwrite the Phase 2
test execution video with the idle research browser recording.
Now skips the rename if qa-session.webm already exists from Phase 2.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/qa-record.ts

@@ -2017,7 +2017,16 @@ async function main() {
       }
 
       knownNames.add(videoName)
-      renameLatestWebm(opts.outputDir, videoName, knownNames)
+      // If Phase 2 already copied a test video as qa-session.webm, don't overwrite it
+      // with the idle research browser video
+      const videoPath = `${opts.outputDir}/${videoName}`
+      if (statSync(videoPath, { throwIfNoEntry: false })) {
+        console.warn(
+          'Phase 2 test video exists — skipping research video rename'
+        )
+      } else {
+        renameLatestWebm(opts.outputDir, videoName, knownNames)
+      }
 
       // Post-process: add TTS narration audio to the video
       if (narrationSegments.length > 0) {