Stop dependabot from opening ruff pre-commit bumps

[albertvillanova]

This PR stops dependabot from opening ruff pre-commit bumps, while leaving the rest of the pre-commit hooks on their weekly schedule.

Motivation

Ruff bumps are pure cost for us. They reformat code and rewrite source through --fix, and they report nothing new under our own rule selection: ruff 0.13.3 and 0.16.4 both pass on every tracked Python file once the rule set is explicit. #6957 is the current example, red on the quality job and rewriting 42 files.

Freezing ruff is a deliberate choice rather than neglect, so it belongs in the config next to the reason, not in dependabot's per-repo dismissal state.

doc-builder bumps stay valuable and must keep flowing. #6956 is a live example.

Solution

Add an ignore entry naming the ruff hook, taken verbatim from the dependency-name that dependabot writes in its own commit trailers. ignore is per dependency, so doc-builder and both github-actions ecosystems are unaffected.

The entry carries no versions or update-types filter, which ignores every update for that dependency. A semver filter would be the natural way to allow patch releases only, but it is not usable here: dependabot does not report an update type for pre-commit hooks, and ruff 0.13.3 is in any case the last release of the 0.13 line, so a patch-only rule would never match anything.

The comment above the entry no longer describes reality once ruff is ignored, so it is reworded to state the remaining rationale for not grouping.

Changes

• Ignore all updates for the ruff pre-commit hook, with a comment recording why
• Reword the stale comment about keeping ruff and doc-builder bumps in separate pull requests

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Note

Low Risk
CI/dependency automation only; no runtime or application code changes.

Overview
Dependabot’s pre-commit ecosystem entry now ignores all updates for https://github.com/astral-sh/ruff-pre-commit, with an inline comment that ruff is frozen on purpose (bumps reformat and --fix without new findings under the project’s rules) and should be bumped manually when needed.

The comment above the ungrouped pre-commit block is reworded so it no longer cites keeping ruff separate from doc-builder; it now says each remaining hook bump should stay reviewable on its own. Weekly pre-commit updates for other hooks (e.g. doc-builder) and github-actions entries are unchanged.

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[bot-ci-comment]

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