ci: add linkspector link checking for blog content, fixes #470

[rfay]

Summary

Adds automated link checking for blog content, mirroring the approach ddev/ddev already uses for its docs (.github/workflows/docs-check.yml + umbrelladocs/action-linkspector).

• .linkspector.yml scopes the check to src/content/blog and ignores a short list of known-noisy patterns (see below).
• .github/workflows/link-check.yml runs linkspector on push to main (full check) and on pull requests (added lines only), same split ddev/ddev uses.

Fixing the internal-link-checker-for-Astro half of #470 (item 1 in the issue, replacing MkDocs strict-build checking) is left for later; root-relative internal links (/contact, /img/...) are intentionally excluded here since Astro has no build-time equivalent yet.

Why the ignore patterns

Running the checker against all 141 existing posts turned up two different kinds of noise that are not actually broken links:

• *.ddev.site example URLs in tutorials always resolve to 127.0.0.1 and never have a real server behind them in CI.
• LinkedIn, Medium, npmjs.com, packtpub.com, private Buildkite build permalinks, and tag1consulting.com all returned errors (403/999) to linkspector headless-browser requests while loading fine in a normal browser, so they are excluded the same way ddev/ddev excludes mailpit.axllent.org and similar in its own config.

Content fixes (26 posts)

Running the checker also surfaced real, pre-existing broken links across the blog archive. Fixed here so the checker starts green on merge instead of red:

• Deleted contributor-training.md (8 posts): that post was removed a while back with a redirect from /blog/contributor-training/ to /blog/category/training/, but the markdown-filename links (contributor-training.md) in these posts still pointed at the deleted file. Repointed to /blog/category/training.
• Broken internal reference / anchor (2 posts): docker-providers.md had a malformed relative link to the ARM64 post; ddev-add-on-maintenance-guide.md linked to a mistyped anchor (#mutagen-problemreport instead of #mutagen-problem-report).
• Renamed/moved targets (4 posts): github.com/ddev/community -> github.com/ddev/.github (the actual community-health repo); two docs.ddev.com pages that were restructured (install/ddev/ -> install/ddev-installation/, alternate-uses/#casual-... -> topics/hosting/); a malformed github.com/.../README URL.
• Dead external pages, archived via Wayback Machine (4 posts): an Ironstar developer survey page (referenced twice), a Florida DrupalCamp session page, and a HelloTech guide page had all been taken down. Replaced with web.archive.org snapshots so the content stays reachable.
• Dead external page, no archive found, de-linked (2 posts): a deleted GitHub Discussion and a personal blog post whose slug changed (fixed to the new slug instead, once I found it).
• Wrong/defunct service (2 posts): xip.io has shut down, replaced with its direct successor sslip.io; frankenphp.org was a wrong TLD, corrected to frankenphp.dev (used correctly elsewhere on the site).
• Malformed URL (1 post): an Unsplash photo-credit link used a broken old-style search URL; replaced with the generic Unsplash referral link used elsewhere for the same purpose.
• Markdown escaping bugs (2 posts): in two places, escaped or missing backticks caused example/loopback URLs (127.0.0.1, an autolinked <http://...>) to be parsed as real hyperlinks instead of inline code. Fixed the markdown so they render as code again.
• Reference to a nonexistent repo (1 post): xdebugctl was linked to a github.com/xdebug/xdebugctl repo that does not exist (it is a script bundled inside DDEV itself, not a separate project); removed that link and kept the working xdebug.org documentation link in the same sentence.

How to test

Since this branch was pushed directly to ddev/ddev.com (not a fork), the new pull_request trigger in link-check.yml should run for this PR itself, not just after merging to main. A separate test repo like ddev-test/ddev.com is not needed: GitHub Actions resolves workflow files for pull_request events from the PR head branch as long as the PR is same-repo, so a brand-new workflow file added in a PR still executes for that PR. Check the "Checks" tab on this PR for a "Link check" run.

To reproduce locally instead:

npm install -g @umbrelladocs/linkspector
linkspector check -c .linkspector.yml -s

That should report 0 failed links (the local run before this PR was opened found 1: a gnu.org navigation timeout that reproduced only in my sandbox and loads fine in an actual browser — worth watching in case it is flaky on CI too, but not treated as broken here).

Fixes #470

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View logs

[stasadev]

Thank you!

I tested it locally with:

~/.ddev-dev-tools/node/bin/linkspector check

There's one more 404 page:
https://staatzstreich.de/blog/wie-ein-kaputter-installer-reload-zu-zwei-open-source-patche-2 (I fixed it).

The check itself is pretty heavy - it checks more than 2,000 links on main. If it becomes too annoying, we could remove it from the main push workflow and run it manually from time to time.