Pin breathe<5 in the Docs workflow

[djkees]

Summary

The Docs workflow will fail on the next push to main. docs.yml installs sphinx and breathe unpinned, so it now picks up breathe 5.0.0 (released 2026-09-21, after this repo's last Docs run), which crashes while rendering the Fortran API page. Pins breathe<5 until that is fixed upstream.

Changes

• docs.yml: pip install sphinx breathe → pip install sphinx "breathe<5", with a one-line comment explaining why

The crash is inside breathe, not CEA (Sphinx 9.1.0):

File ".../breathe/renderer/sphinxrenderer.py", line 480, in get_definition_without_template_args
    if len(data_object.bitfield) > 0:
TypeError: object of type 'NoneType' has no len()

docs.yml only triggers on push to main, so PR checks will not exercise this change. When the build fails the deploy job is skipped, so the docs site silently stops updating.

Testing

• Reproduced and fixed in the fork (Pin breathe<5 in the Docs workflow djkees/cea#303): before the pin, Docs failed on every fork main push after 2026-09-21; after it, the Docs run on fork main passed end to end (build and deploy): https://github.com/djkees/cea/actions/runs/36164575747
• That run installed breathe 4.36.0 with Sphinx 9.1.0 and "Build Sphinx HTML" reported build succeeded.

Compatibility / Numerical behavior

• No expected changes to numerical results

---

Drafted with Claude's assistance.

• Confirmed the failure cause from the failed run's log (traceback above) and checked PyPI: breathe 5.0.0 was released 2026-09-21T18:50Z; this repo's last Docs run (2026-09-21T14:21Z) predates it, so upstream has not yet hit the failure.
• Verified the fix by reading the passing fork run's log for the installed versions (breathe-4.36.0, sphinx-9.1.0) and the build succeeded line, and confirmed the run's overall conclusion was success, rather than relying on job status alone.
• Confirmed the diff is a single command line plus its comment in docs.yml (git diff upstream/main..HEAD).

🤖 Generated with Claude Code