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 documentation files to catch broken URLs in pull requests and on a weekly schedule.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: b60916a7-0751-45d2-ab25-949673e5fb61

📥 Commits

Reviewing files that changed from the base of the PR and between c3bde44 and 0d8d8f6.

📒 Files selected for processing (1)

• .github/workflows/link-check.yml

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📝 Walkthrough

Walkthrough

This pull request adds a new GitHub Actions workflow for automated link checking. The .github/workflows/link-check.yml file defines a link-check workflow that uses the lychee link checker action to scan markdown files for dead URLs. The workflow runs on pull requests, pushes to the main branch, a weekly Monday schedule, and manual triggers. It sets read-only permissions, checks out the repository, and runs lychee with concurrency limits, email link exclusions, and specific accepted HTTP status codes, without failing the workflow on findings.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description lacks the required template structure with Summary, Test plan, and Related sections specified in the repository's template.	Restructure the description to match the repository template: add a Summary section, provide a Test plan checklist with happy-path and edge cases, and include a Related section with relevant 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 CI workflow for link checking using the lychee tool.
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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