ci: Trigger doc release on stable release

[vdusek]

Summary

• The stable release pipeline was missing a doc release step, so the changelog on the website was not updated after a stable release
• Added a doc_release job to manual_release_stable.yaml (same pattern as doc_release_post_publish in on_master.yaml)
• The job runs after changelog_update and pypi_publish, using the changelog commit ref to include the updated changelog

Test plan

• Verify the workflow YAML is valid
• Trigger a stable release and confirm doc release runs

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.47%. Comparing base (c0a74b9) to head (3cc7b18).
⚠️ Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #798      +/-   ##
==========================================
- Coverage   85.50%   85.47%   -0.04%     
==========================================
  Files          46       46              
  Lines        2691     2691              
==========================================
- Hits         2301     2300       -1     
- Misses        390      391       +1     

Flag	Coverage Δ
e2e	35.48% <ø> (ø)
integration	57.63% <ø> (+0.03%)	⬆️
unit	72.38% <ø> (-0.08%)	⬇️

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