Add internal link checker for documentation

[josbeir]

This PR adds automated validation of internal markdown links with baseline support for existing issues.

Changes

Link Checker Script (bin/check-links.js)

• Validates internal file references and anchor links
• Zero dependencies (Node.js built-ins only)
• Supports glob patterns: "docs/**/*.md"
• Baseline filtering to ignore known issues (opt-in)

CI Integration (.github/workflows/docs-validation.yml)

• Added link-check job
• PRs: Checks only changed files
• Uses baseline to focus on new issues only

Baseline (.github/linkchecker-baseline.json)

• 421 existing broken links cataloged
• Opt-in via --baseline flag

Usage

# Check files
node bin/check-links.js docs/en/installation.md
node bin/check-links.js "docs/**/*.md"

# With baseline
node bin/check-links.js --baseline .github/linkchecker-baseline.json "docs/**/*.md"

[Copilot]

Pull request overview

Adds an internal Markdown link checker and integrates it into CI to prevent introducing new broken internal links while tolerating existing known issues via a baseline.

Changes:

• Added a zero-dependency Node.js link-checker (bin/check-links.js) with optional baseline filtering and baseline generation.
• Integrated link checking into the documentation validation GitHub Actions workflow.
• Added contributor documentation for running the link checker locally and committed a baseline of existing issues.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 2 comments.

File	Description
docs/en/contributing/documentation.md	Documents how to run the new link checker and adds it to the local pre-flight command list.
bin/check-links.js	Implements internal link validation, globbing, anchor resolution, and baseline filtering/generation.
.github/workflows/docs-validation.yml	Adds a new CI job to run the link checker (baseline-enabled) on changed markdown files.
.github/linkchecker-baseline.json	Stores the catalog of known broken links for baseline filtering.

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