[albertvillanova]

This PR documents, in the "Dependency version floors" section of the contributing guide, that the minimum-versions CI job pins every dependency at its floor, so a floor change also updates the pin.

Motivation

After #7741 the job runs on the oldest supported Python, so its pins are exactly the pyproject.toml floors. Without a written rule, a floor bump can update pyproject.toml and leave the CI pin behind, so the new floor is never tested.

Changes

• Add a sentence to "Dependency version floors" in CONTRIBUTING.md stating that the minimum-versions job pins every floor, and that a floor change updates its pin

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Note

Low Risk
Documentation-only change to CONTRIBUTING.md with no runtime or CI behavior changes.

Overview
Documents contributor workflow for dependency version floors: the minimum-versions CI job installs each dependency at its declared floor, so raising a floor in pyproject.toml must include updating that job’s pins or the new minimum is never exercised in CI.

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[bot-ci-comment]

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[albertvillanova]

I dropped "runs on the oldest supported Python" from the sentence: #7743 now states it in the "Python versions" section, next to the rule to move the job when a version is dropped. Keeping it here as well would say the same thing twice in adjacent sections, and the two copies could drift. This section keeps only the floor-side rule: a floor change also updates its pin.

[qgallouedec]

Thanks, to merge after #7741