Separate stable and dev documentation deployments with version switcher

[Copilot]

• Fix release in docs/source/conf.py to distinguish dev vs stable using BUILD_DEV_HTML env var
• Add version switcher configuration to html_theme_options in conf.py
• Fix linkcode_resolve to use correct branch (develop for dev, master for stable)
• Update html_baseurl and github_version in conf.py to be branch-aware
• Create docs/source/_static/switcher.json with stable and dev version entries
• Update .github/workflows/docs.yml to set BUILD_DEV_HTML=1 on develop branch builds
• Rename and split deploy jobs: develop → docs/dev/, master → docs/ (stable) for both neurotechx and gh-pages
• Add changelog entry to docs/source/whats_new.rst
• Run pre-commit on all changed files (fixed JSON formatting in switcher.json)

Original prompt

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This section details on the original issue you should resolve

<issue_title>Development and stable version webpage</issue_title>
<issue_description>At the moment, we have dev as the stable version. This lead to situation where people have mismatched with pip version and what the documentation is showing.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Development and stable version webpage #983

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[bruAristimunha]

Ignore the braindecode test and fix the other issues please.

[bruAristimunha]

@copilot, address the comments above

[Copilot]

@copilot, address the comments above

Fixed in 39c1d48 — added the missing changelog entry to docs/source/whats_new.rst, which resolves the "Check What's News Changes" CI failure. The braindecode test failure is unrelated to these changes and pre-exists on the develop branch.

[bruAristimunha]

Pre commit please @copilot

[Copilot]

Pre commit please @copilot

Done in 291ef12 — ran pre-commit on all changed files. The only fix needed was reformatting switcher.json to use 4-space indentation (required by the pretty-format-json hook). All other hooks (black, isort, ruff, codespell, etc.) passed without changes.