chore(trace-viewer): show only the screencast frame on timeline hover

[Pavel Feldman (pavelfeldman)]

Summary

• Timeline hover popup now shows just the screencast frame; the action/locator title under it is gone.
• Popup no longer renders an empty box when there is no frame for the hovered time.

[github-actions]

Test results for "tests 1"

20 flaky

⚠️ [chromium-library] › library/global-fetch.spec.ts:293 › should return security details from response `@frozen-time-library-chromium-linux`
⚠️ [chromium-library] › library/har.spec.ts:639 › should have security details `@frozen-time-library-chromium-linux`
⚠️ [chromium-library] › library/global-fetch.spec.ts:293 › should return security details from response `@chromium-ubuntu-22.04-arm-node20`
⚠️ [chromium-library] › library/har.spec.ts:639 › should have security details `@chromium-ubuntu-22.04-arm-node20`
⚠️ [chromium-library] › library/video.spec.ts:664 › screencast › should capture full viewport `@chromium-ubuntu-22.04-arm-node20`
⚠️ [chromium-library] › library/global-fetch.spec.ts:293 › should return security details from response `@realtime-time-library-chromium-linux`
⚠️ [chromium-library] › library/har.spec.ts:639 › should have security details `@realtime-time-library-chromium-linux`
⚠️ [chromium-library] › library/video.spec.ts:356 › screencast › should work for popups `@realtime-time-library-chromium-linux`
⚠️ [chromium-library] › library/global-fetch.spec.ts:293 › should return security details from response `@chromium-ubuntu-22.04-node24`
⚠️ [chromium-library] › library/har.spec.ts:639 › should have security details `@chromium-ubuntu-22.04-node24`
⚠️ [chromium-library] › library/video.spec.ts:736 › screencast › should work with video+trace `@chromium-ubuntu-22.04-node24`
⚠️ [chromium-library] › library/global-fetch.spec.ts:293 › should return security details from response `@chromium-ubuntu-22.04-node20`
⚠️ [chromium-library] › library/har.spec.ts:639 › should have security details `@chromium-ubuntu-22.04-node20`
⚠️ [chromium-library] › library/video.spec.ts:294 › screencast › should capture navigation `@chromium-ubuntu-22.04-node20`
⚠️ [chromium-library] › library/global-fetch.spec.ts:293 › should return security details from response `@chromium-ubuntu-22.04-node22`
⚠️ [chromium-library] › library/har.spec.ts:639 › should have security details `@chromium-ubuntu-22.04-node22`
⚠️ [firefox-library] › library/global-fetch.spec.ts:293 › should return security details from response `@firefox-ubuntu-22.04-node20`
⚠️ [firefox-library] › library/har.spec.ts:639 › should have security details `@firefox-ubuntu-22.04-node20`
⚠️ [webkit-library] › library/global-fetch.spec.ts:293 › should return security details from response `@webkit-ubuntu-22.04-node20`
⚠️ [webkit-library] › library/har.spec.ts:639 › should have security details `@webkit-ubuntu-22.04-node20`

51119 passed, 1226 skipped

---

Merge workflow run.

[github-actions]

Test results for "MCP"

1 failed
❌ [firefox] › mcp/annotate.spec.ts:446 › should switch screencast to -s session on show --annotate @mcp-windows-latest-firefox

8100 passed, 1311 skipped

---

Merge workflow run.

[github-actions]

Hi, I'm the Playwright bot and I took a first look at the CI failures here.

🟢 CI is clear — the one failure is a known Firefox flake

The only real failure, mcp/annotate.spec.ts:446 on mcp-windows-latest-firefox, is a pre-existing flake unrelated to this trace-viewer change. Everything else is flaky/passed.

Details

This PR only touches trace-viewer UI (filmStrip.tsx/.css, timeline.tsx, workbench.tsx) to change the timeline hover popup. It doesn't reach the MCP annotate/screencast code path.

Pre-existing flake / infra

• [firefox] › mcp/annotate.spec.ts:446 › should switch screencast to -s session on show --annotate (@mcp-windows-latest-firefox) — pre-existing flake. In the aggregated CI results this test's Firefox verdict flips between runs: failed 30 of 717 runs (~4%), passed the other 687, and those failures span 33 distinct SHAs across 21 different PRs — none of them this PR's head. Chromium/WebKit/Chrome barely see it (9/726, 3/733, 2/731). The diff here is trace-viewer only, so it can't be the cause.

No real failures

• The "tests 1" report has 0 failed — 20 flaky (all global-fetch/har security-details and video screencast entries that passed on retry) and 51119 passed. Nothing to attribute to this PR.

_{Triaged by the Playwright bot - agent run}