Context

The README hero currently uses a very generic demo GIF alt text. A more specific alt text would make the project clearer in screen readers and plain-text previews without changing any assets.

Scope

• Update the README image alt text for docs/demo.gif to describe the BrowserTrace demo, failed browser-agent timeline, and first red step.
• Keep the same docs/demo.gif file path. Do not replace or regenerate media assets.
• Add or update a focused assertion in tests/test_metadata.py so the README alt text stays descriptive.

Acceptance criteria

• The README no longer uses ![demo](docs/demo.gif).
• The new alt text mentions BrowserTrace and a failed browser-agent trace/timeline.
• The change is docs/test 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.