Upgrade setup-python and Codecov actions for Node 24 runners

[konard]

Summary

Fixes #32.

• Upgrade all eight actions/setup-python references from v5 to v6 across the release and docs workflows.
• Upgrade the gated Codecov upload from codecov/codecov-action@v4 to v7.
• Add workflow policy assertions for the required current majors and explicitly reject the outdated majors.
• Add a changelog fragment and remove the autogenerated branch placeholder.

Reproduction

Before the workflow updates, the new policy assertions fail in three places: the release workflow contains zero setup-python@v6 references, the docs workflow contains zero setup-python@v6 references, and the gated Codecov step still uses v4 instead of v7.

Verification

• .venv/bin/python -m pytest tests/test_workflows.py -q (13 passed)
• .venv/bin/python -m pytest --cov=src --cov-report=term (44 passed, 100% package coverage)
• .venv/bin/ruff check .
• .venv/bin/ruff format --check .
• .venv/bin/mypy src/
• .venv/bin/python scripts/check_file_size.py
• .venv/bin/sphinx-build -W --keep-going -b html docs _site
• .venv/bin/python -m build
• .venv/bin/twine check dist/*
• git diff --check

mypy passed with the repository's existing warnings about its Python 3.9 target and deprecated strict_concatenate setting.

[konard]

Working session summary

Implemented and finalized PR #36.

• Upgraded all actions/setup-python pins to v6.
• Upgraded codecov/codecov-action to v7.
• Added regression policy tests rejecting old majors.
• Added a changelog fragment.
• Pushed commit 1dd83cb.
• Updated the PR title/description and marked it ready for review.
• Fresh CI and Docs workflows passed on the pushed commit.
• Local suite: 44 tests passed with 100% package coverage; lint, formatting, mypy, docs, build, and package validation passed.

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[konard]

🤖 Solution Draft Log

This log file contains the complete execution trace of the AI solution draft process.

💰 Cost estimation:

• Model: GPT-5.6 Sol
• Provider: OpenAI
• Public pricing estimate: $1.927913

📊 Context and tokens usage:

• 55.0K / 200K (28%) input tokens, 7.3K / 128K (6%) output tokens

Total: (55.0K + 1.1M cached) input tokens, 7.3K output tokens, $1.927913 cost

🤖 Models used:

• Tool: OpenAI Codex
• Requested: gpt-5.6-sol
• Thinking level: off (disabled)
• Model: GPT-5.6 Sol (gpt-5.6-sol)

📎 Log file uploaded as Gist (902KB)

• View complete solution draft log

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Now working session is ended, feel free to review and add any feedback on the solution draft.

[konard]

🔄 Auto-restart 1/5

Detected uncommitted changes from previous run. Starting new session to review and commit or discard them.

Uncommitted files:

?? ci-logs/

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[konard]

Working session summary

Issue #32 is fully implemented and finalized in PR #36.

• Upgraded all setup-python references to v6 and Codecov to v7.
• Added workflow regression-policy tests and changelog fragment.
• Local validation passed: 44 tests, 100% package coverage, lint, formatting, mypy, docs, build, and Twine checks.
• CI/CD and Docs passed for current SHA 1dd83cb.
• PR is ready for review and cleanly mergeable.
• Removed the generated ci-logs/ artifacts; working tree is clean.
• Branch is current with main and synchronized with its remote.

---

This summary was automatically extracted from the AI working session output.

[konard]

🔄 Auto-restart 1/5 Log

This log file contains the complete execution trace of the AI solution draft process.

💰 Cost estimation:

• Model: GPT-5.6 Sol
• Provider: OpenAI
• Public pricing estimate: $0.396937
• Token usage: 38,387 input, 3,659 output, 0 reasoning, 190,464 cache read

🤖 Models used:

• Tool: OpenAI Codex
• Requested: gpt-5.6-sol
• Model: GPT-5.6 Sol (gpt-5.6-sol)

📎 Log file uploaded as Gist (1474KB)

• View complete solution draft log

---

Now working session is ended, feel free to review and add any feedback on the solution draft.

[konard]

🎉 Auto-merged

This pull request has been automatically merged by hive-mind.

• All CI checks have passed

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Auto-merged by hive-mind with --auto-merge flag