ci: add link-check workflow (lychee)

[satyakwok]

Same pattern as the link-check workflow already shipped to awesome-sentrix, whitepaper, canonical-contracts, and dapp-starter. Lychee scans every markdown link on PR + push to main + weekly Monday 03:00 UTC cron. Non-blocking — mirrors the gitleaks workflow's policy.

Summary by CodeRabbit

• Chores
  • Added automated link validation for markdown documentation to ensure all links remain functional and accessible.

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

This pull request adds a new GitHub Actions workflow file that implements automated link checking for the repository. The workflow runs lychee against all markdown files on pull requests, pushes to the main branch, and a weekly Monday schedule. The configuration uses pinned action versions, excludes mail-related links, allowlists specific HTTP status codes, and operates in non-blocking mode so link check findings do not cause workflow failure.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The PR description explains the purpose and context but lacks the required structure from the template (Summary, Test plan, Related sections).	Restructure the description to follow the template: add a Summary section, include a Test plan with test cases, and add a Related section with relevant issue/PR links.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'ci: add link-check workflow (lychee)' clearly and concisely describes the main change: adding a new CI workflow for link checking.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ci/link-check

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