chore(engine): drop stale fork-branch reference from test comment

The screenshotService.test.ts regression-suite comment pointed at the
author's fork branch as backstory. Strip the line so upstream code
doesn't carry a fork-relative reference; the surrounding paragraph
already explains the bug end-to-end without it.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/engine/src/services/screenshotService.test.ts

@@ -202,7 +202,6 @@ describe("video-frame injection respects ancestor visibility", () => {
   // injected `data-start="0"` + probed full-source duration cover the
   // whole timeline), so the bug produced one full-bleed speaker overlay
   // per inactive sub-comp — covering whichever moment was actually visible.
-  // See: https://github.com/lirian-su-opus/hyperframes branch issue thread.
 
   type StyleLike = {
     display?: string;