Add release-tag broken-link quality ledger workflow

[Copilot]

Pull Request Template: Add a Conference or Workshop

Thank you for contributing! Most PRs are to add a new conference or workshop. The following are to help ensure you've added everything correctly:

This PR implements Phase 2 link-integrity tracking by running automated broken-link scans on v* release tags (and manual dispatch), then appending versioned results to a persistent quality ledger in _data/quality_log.yml.

Conference/Workshop Details

• Name, Location, Date(s), Website URL and Status are required
• X / Twitter is Optional
• Location should be City + Country or Online
• Status can include information about registration, pricing, calls for proposals and can include links to all the above.

Checklist

• I have added the conference/workshop to the correct YAML file (_data/current.yml or _data/past.yml)
• The entry includes name, location, date(s), url and accurate status
• The entry is in chronological order (soonest to furtherest away)
• If there are any special characters in the name field (: or ; or '), the name must be in quotes (")
• I have checked for duplicates to avoid listing the same event twice
• Build runs successfully

Additional context

• Workflow

  • Added .github/workflows/quality-links.yml to trigger on push.tags: v* and workflow_dispatch.
  • Builds _site, runs linkinator, emits broken-link totals in CI logs, and fails clearly when broken links are present.

• Quality ledger persistence

  • Added tools/append_quality_log.rb to append (not overwrite) entries in _data/quality_log.yml.
  • Entry schema includes version, release_date, commit_sha, broken_links, workflow_run_url, plus stable placeholder fields for other Phase 2 metrics.

• Data file + focused coverage

  • Added _data/quality_log.yml as the ledger store.
  • Added test/append_quality_log_test.rb for append behavior and invalid count handling.

# .github/workflows/quality-links.yml (excerpt)
on:
  push:
    tags: ['v*']
  workflow_dispatch:

# appender invocation
ruby tools/append_quality_log.rb \
  --version "$VERSION" \
  --broken-links "$BROKEN_COUNT" \
  --commit-sha "$COMMIT_SHA" \
  --workflow-run-url "$WORKFLOW_RUN_URL" \
  --output _data/quality_log.yml

• Fixes Phase 2: Implement Broken Link Checker for Quality Ledger #931