Add repository validation and restore VSS workshop ingress manifest

[harmke]

Summary

Add repository-wide quality checks and restore the ingress manifest referenced by the VSS workshop.

Changes include:

• Add pre-commit checks for whitespace, line endings, merge conflicts, YAML, Markdown formatting, and documentation links.
• Add a GitHub Actions workflow that runs pre-commit on pull requests.
• Pin pre-commit to the tested version.
• Add timeout and retry handling for external link validation.
• Add generic repository guidance in AGENTS.md.
• Restore the missing VSS ingress manifest from repository history.
• Fix existing Markdown formatting and broken or case-mismatched links.
• Remove the PR template link to the nonexistent CLA.MD; DCO sign-off remains required.
• Document local validation commands for contributors.

Related Issue(s)

N/A

Type of Change

• New sample
• Update to existing sample
• Bug fix
• Documentation
• Infrastructure / CI
• Other (describe below)

Testing

The following checks pass:

pre-commit run --all-files
git diff --check

This includes:

• YAML validation
• Markdown linting
• Internal and external link validation
• Whitespace and line-ending checks
• Merge-conflict marker detection

The full pre-commit suite was run repeatedly and produced no additional changes.

Checklist

• My commits are signed off (git commit -s)
• I have read CONTRIBUTING.md
• I have updated documentation where relevant
• I have verified the affected sample runs end-to-end, or explained why that was not possible

[azeltov]

i like the new pre-commit changes. Lets use it.