Revisit CI check-docs + /devel/generate-developer-api-docs

[joverlee521]

Context

Following up on comments in #1762

Currently the CI does a fresh install of the dev dependencies during the check-docs job and flags changes in the API docs that need to be regenerated. However, if devs do not have a fresh environment locally, then they may not see the same changes when running /devel/generate-developer-api-docs (e.g. #1760 (comment)).

Possible solutions

1. Document the need to run /devel/generate-developer-api-docs in a fresh environment
2. Add upper pins to dev dependencies. This would guard us against upstream breakages like _stringify_annotation patch breaks in Sphinx==8.2.0 tox-dev/sphinx-autodoc-typehints#523 and devs would only need to update their local envs when the pins are updated. However, then we'd have to deal with the churn of updating the dependency pins as needed.
3. Update /devel/generate-developer-api-docs to create it's own venv before regenerating the docs
4. others?