ci(security): add dependency and code scanning

[cameroncuster]

Summary

• add weekly grouped Dependabot updates for pnpm dependencies and GitHub Actions
• add CodeQL JavaScript/TypeScript analysis on pull requests, main pushes, and a weekly schedule
• use least workflow permissions and build-free CodeQL analysis
• preserve the required Node 24 CI gate and non-blocking Node 26 probe unchanged

Verification

• YAML parsed successfully
• Prettier passed
• ESLint passed
• Svelte check passed
• unit tests: 184/184 passed
• workflow permission, trigger, and runtime invariants validated
• independent workflow review blocker resolved

---

Pull Request opened by Augment Code | View session

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
gitgud	Ready	Preview, Comment	Jul 23, 2026 9:20pm

[github-advanced-security]

You are seeing this message because GitHub Code Scanning has recently been set up for this repository, or this pull request contains the workflow file for the Code Scanning tool.

What Enabling Code Scanning Means:

• The 'Security' tab will display more code scanning analysis results (e.g., for the default branch).
• Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results.
• You will be able to see the analysis results for the pull request's branch on this overview once the scans have completed and the checks have passed.

For more information about GitHub Code Scanning, check out the documentation.