Add pre-commit hooks for gofmt and staticcheck

[koba-e964]

Summary

• add repo-pinned pre-commit hooks for gofmt and staticcheck
• document pre-commit usage in README

Testing

• pre-commit run --all-files

[Copilot]

Pull request overview

Adds pre-commit tooling so contributors can automatically run Go formatting and linting checks locally, and documents how to use it.

Changes:

• Add a repo-pinned .pre-commit-config.yaml with hooks for gofmt and staticcheck.
• Document pre-commit installation and usage in README.md.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
README.md	Documents local development workflow using pre-commit for gofmt and staticcheck.
.pre-commit-config.yaml	Adds pinned pre-commit hooks to enforce formatting and linting before commits.

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