⬆️ Require CMake 3.28 and reduce dependency builds

[burgholzer]

🤖 AI text below 🤖

Description

Raise the minimum CMake version to 3.28, replace the conditional module-scanning workaround with the global setting, and use native FetchContent EXCLUDE_FROM_ALL/SYSTEM support for Core, JSON, and Taskflow. Remove the now-redundant Taskflow include-property rewrite and update the requirements documentation.

Prepared with GPT-5/Codex assistance under explicit maintainer authorization.

Validation

• uvx nox -s lint
• Release configure/build with CMake 4.4.2 and exactly 3.28.4
• 124 unaffected tests pass with each version
• The remaining stochastic test failure reproduces unchanged on origin/main (265 versus 211 ± 50)
• Confirmed CMake 3.27 rejects configuration

Checklist

• The pull request only contains commits that are focused and relevant to this change.
• I have added appropriate tests that cover the new/changed functionality.
• I have updated the documentation to reflect these changes.
• I have added entries to the changelog for any noteworthy additions, changes, fixes, or removals.
• I have added migration instructions to the upgrade guide (if needed).
• The changes follow the project's style guidelines and introduce no new warnings.
• The changes are fully tested and pass the CI checks.
• I have reviewed my own code changes.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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