Improve CI workflows and fix documentation deployment

[AndrewSazonov]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.15%. Comparing base (56b35da) to head (5fc090b).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #117   +/-   ##
========================================
  Coverage    83.15%   83.15%           
========================================
  Files           89       89           
  Lines         5455     5455           
  Branches       452      452           
========================================
  Hits          4536     4536           
  Misses         753      753           
  Partials       166      166           

Flag	Coverage Δ
integration	69.93% <ø> (ø)
unittests	73.34% <ø> (ø)

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[Copilot]

Pull request overview

This PR refactors and improves CI workflows, focusing on documentation deployment and backmerge automation. The changes streamline workflow execution, fix command references, and replace the PR-based backmerge approach with a direct merge strategy.

Key changes:

• Replaced PR-based backmerge workflow with direct master→develop merge on version tags
• Improved documentation deployment by explicitly fetching gh-pages branch and adjusting concurrency settings
• Updated PyPI test workflow to use correct CLI command and copy pytest.ini configuration

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
.github/workflows/pypi-test.yaml	Removed redundant PyPI install step (already in pixi.toml), added pytest.ini copy, updated CLI command from fetch-tutorials to download-all-tutorials
.github/workflows/docs.yaml	Enhanced comments throughout, changed concurrency to prevent race conditions, removed fetch-depth from checkout, added explicit gh-pages branch fetch
.github/workflows/backmerge.yaml	New workflow implementing direct master→develop merge (replaces PR-based approach), uses GitHub App authentication to bypass branch protection
.github/workflows/backmerge-pr.yaml	Removed in favor of simpler direct merge approach in backmerge.yaml

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