Context

The debugging walkthrough embeds docs/demo.mp4 with docs/demo-poster.png and a fallback download link. A short accessible label or nearby caption would help screen-reader users and plain-text reviewers understand what the video shows without playing it.

Scope

• Update docs/debug-browser-agent-failure.html around the demo video only.
• Keep the same docs/demo.mp4 and docs/demo-poster.png; do not replace or regenerate media assets.
• Describe BrowserTrace, the failed browser-agent trace/timeline, and the first red step.
• Keep the copy concise and consistent with the existing page style.

Acceptance criteria

• The embedded demo video has descriptive accessible context, such as an aria-label, a figcaption, or nearby explanatory text.
• The description mentions BrowserTrace and a failed browser-agent trace/timeline.
• The change is docs/html only and stays small.

Verification

Run:

uv run --python 3.11 --extra dev pytest tests/test_metadata.py -q

No stars, upvotes, reposts, or reciprocal promotion are requested.