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 92.28%. Comparing base (202b500) to head (91b14ed).
⚠️ Report is 5 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1758      +/-   ##
==========================================
+ Coverage   92.26%   92.28%   +0.01%     
==========================================
  Files         156      156              
  Lines       10644    10644              
==========================================
+ Hits         9821     9823       +2     
+ Misses        823      821       -2     

Flag	Coverage Δ
unit	92.28% <ø> (+0.01%)	⬆️

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