Add pre-commit git hook to run lintrunner on staged files (#28013)
### Description
Add a pre-commit [git
hook](https://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks) 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 https://github.com/microsoft/onnxruntime/pull/27856.
Catching lint issues at commit time saves CI cycles and review time.