Context

Rex flagged in the PR #1 review (suggestion S11 + answer to question #11) that apexstack doesn't currently dogfood its own stack — there are no CI checks running on the apexstack repo even though it ships seven golden-path pipelines for adopters.

Defensible for v0.1 (content-only repo, nothing to typecheck), but the drift Rex caught in PR #1 (B3 hero metric, B4 tree counts, B5 Sentinel/Scout naming, S1 dead anchor) would have been caught earlier by linters and link-checkers.

Acceptance Criteria

Add the following GitHub Actions workflows under `.github/workflows/`:

• `pr-title-check.yml` — copy from `golden-paths/pipelines/pr-title-check.yml`. Enforces ticket ID in PR titles.
• `markdown-lint.yml` — run `markdownlint-cli2` on `**/*.md`. Catches broken markdown and inconsistent headings.
• `shellcheck.yml` — run `shellcheck` on `.claude/hooks/*.sh`. Catches portability bugs in hook scripts.
• `link-check.yml` — run `lychee` on `site/index.html` and `**/*.md`. Would have caught the dead `#stack` anchor in PR feat(#1): initial ApexStack project #1.
• (Optional) `html-validate.yml` — run `html-validate` on `site/index.html`. Catches accessibility regressions.

Why v0.2 not v0.1

• Keeps PR feat(#1): initial ApexStack project #1 scope clean (already 11k+ lines, already bundles 3 concerns in `ba892bc`)
• Lets us iterate on linter configs without churning the initial release
• Each workflow is independent and can land in its own small PR

Links

• PR feat(#1): initial ApexStack project #1: feat(#1): initial ApexStack project #1
• Existing golden path: `golden-paths/pipelines/pr-title-check.yml`