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
  • Implemented automated link validation workflow to scan documentation files for broken links. Configured to run on pull requests, main branch updates, weekly schedules, and manual dispatch with comprehensive status reporting to maintain documentation integrity.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: d21c2499-5a77-43cf-9953-754811f220cc

📥 Commits

Reviewing files that changed from the base of the PR and between 6dd4c8c and 2210bd7.

📒 Files selected for processing (1)

• .github/workflows/link-check.yml

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📝 Walkthrough

Walkthrough

This PR introduces a new GitHub Actions workflow for automated link checking across documentation. The link-check workflow runs the lycheeverse/lychee-action tool to scan all Markdown files (**/*.md) for broken links. The workflow triggers on pull requests, pushes to the main branch, a weekly Monday schedule at 03:00 UTC, and manual dispatch. The lychee job runs on ubuntu-22.04, accepts HTTP status codes 200, 206, 403, and 429 as valid, and is configured to never fail the workflow on link validation findings.

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 description is incomplete. It lacks the required 'Summary' and 'Test plan' sections specified in the repository template, providing only informal context without structured information.	Add a structured summary explaining what changed and why, and include a test plan with a bulleted checklist of verification steps (happy-path and edge cases).

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'ci: add link-check workflow (lychee)' clearly and concisely summarizes the main change: adding a new 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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