Add pre-commit git hook to run lintrunner on staged files

[vraspar]

Description

Add a pre-commit git hook that runs lintrunner on staged files, catching lint and formatting issues before they reach CI.

The hook runs lintrunner in check-only mode (no auto-fix) to avoid issues with partial staging. If lint issues are found, the commit is blocked and the developer is prompted to run lintrunner -a to fix.

The hook is opt-in. Contributors enable it with: git config core.hooksPath .githooks

Motivation and Context

Follow-up from #27856. Catching lint issues at commit time saves CI cycles and review time.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds an opt-in Git pre-commit hook that runs lintrunner against the files being committed, aiming to catch lint/format issues earlier and reduce CI churn.

Changes:

• Document how to enable/bypass the repo-provided Git hooks via core.hooksPath.
• Add a .githooks/pre-commit script that runs lintrunner in check-only mode and blocks commits on failure.
• Ensure .githooks uses LF line endings via .gitattributes.

Reviewed changes

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

File	Description
CONTRIBUTING.md	Documents enabling the pre-commit hook and basic usage/bypass guidance.
.githooks/pre-commit	Implements a pre-commit hook that runs lintrunner on paths from the index.
.gitattributes	Forces LF endings for hooks to work consistently across platforms.

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[edgchen1]

thanks for adding this!