feat: Add AI BIDS assistant widget to the specification pages

[yarikoptic]

Add an interactive assistant widget that appears on all MkDocs pages, allowing users to access the BIDS assistant (https://bids-assistant.neurosift.app/) via a floating button and iframe.

Assistant's code etc are at
https://github.com/magland/qp/tree/main/src/assistants/bids-assistant
and is really crude and could be improved but it seems already to provide very reasonable assistance! Please try it out (let's see if works while in preview!)

Changes:

• Add theme override template (src/overrides/main.html) extending Material theme
• Add assistant widget styling (src/css/assistant.css) with responsive design
• Configure custom theme directory and include assistant CSS in mkdocs.yml
• Implement lazy loading of assistant iframe on first click

🤖 Generated with Claude Code

Code snippet is based on the one for NWB which could be seen in

• Update iframe source URL for NWB Assistant chat NeurodataWithoutBorders/pynwb#2140
• preview URL: https://bids-specification--2254.org.readthedocs.build/en/2254/

TODOs

• adjust styling / placement -- potentially just along the "Social" buttons there?

ATM looks like

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.83%. Comparing base (373da35) to head (c19ada6).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2254   +/-   ##
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  Coverage   82.83%   82.83%           
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  Files          20       20           
  Lines        1672     1672           
=======================================
  Hits         1385     1385           
  Misses        287      287           

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[bendichter]

I recommend opening in a separate window like https://neuroconv.readthedocs.io/en/stable/
the UX for the iframe chat UI is tricky because you lose the chat history when you change the page

[julia-pfarr]

How about letting users try this at the EBRAINS summit and collect feedback on where it should be placed?

[bendichter]

I think it's fine as-is. I would recommend adding a button to pop the chat out as a separate window, but that requires a PR on a different repo: magland/qp#23

[neuromechanist]

Also look at this: https://demo.osc.earth/bids
It knows about PRs, Issues, BIDS references, and even the references that cited the BIDS reference papers, all through a YAML file. Repo is at: https://github.com/OpenScience-Collective/osa
The Assistant can even get context from the page your on to provide a better response.

You can resize the widget (drag from top left), make a pop out, or change the model with BYOK.

It needs ~10 lines added to the target frontend (with additional configs for colors, logos, etc):

<script src="https://osa-demo.pages.dev/osa-chat-widget.js"></script>
<script>
  OSAChatWidget.setConfig({
    communityId: 'hed'  // or 'bids', 'eeglab', etc.
  });
</script>

[yarikoptic]

I will consider it superseded by @neuromechanist 's

• Add Open Science Assistant (OSA) BIDS chat widget #2442