Add a GIF/video to CONTRIBUTING.md showing first-contribution workflow

[rajkumarsakthivel]

Record a short GIF or video showing the contributor workflow from clone to passing tests.

Why: A visual walkthrough removes uncertainty for first-time contributors. Seeing the actual terminal output (clone, install, run tests, make a change) is more inviting than reading steps.

Steps:

1. Record a terminal session (~60s) showing:
   • `git clone` the repo
   • `uv sync` or `pip install -e .`
   • `pytest` (all tests pass)
   • Make a small change, run tests again
2. Convert to GIF (tools: vhs, asciinema, or screen recording + gifski)
3. Add to CONTRIBUTING.md at the top
4. Keep file size under 2MB (link to a longer video if needed)

Deliverable: A GIF embedded in CONTRIBUTING.md showing the dev setup workflow.