chore: add automated labeler to PRs

[AdamJ]

Summary

Add a GitHub workflow configuration to automatically apply certain labels to pull requests, based on the changed files.

Type of Change

• New feature
• Update to existing feature
• Bug fix
• Documentation update
• Other (describe below)

Related Issue

Closes #

Changes Made

• Add .github/labeler.yml for applying labels based on changed files
• Add .github/workflows/labeler.yml to run the labeler checks

Checklist

Complete all items that apply to your change. Check N/A for items that don't apply.

Documentation

Run sync-docs skill with Claude Code to automatically update relevant files.

• Any notable changes added to the README.md
• CHANGELOG.md updated accordingly
• N/A — no README changes

General

• Branch is up to date with main
• No unrelated files included in this PR
• Tested locally by invoking the npm run test, npm run lint, and npm run build

Notes for Reviewers