Remove an unused template and primitive, fix three stale claims

Andrew Dunnrequested to merge
templates/truth into main

What does this MR do and why?

Deletes a template nothing references and a primitive nothing calls, and corrects three claims that name markup or files the code does not have. standards/design/templates/single-file-site.html is removed: its asset URLs omitted the /design/ segment the Pages CDN publishes under, and it loaded mermaid from a third-party origin the design principles exclude. check_toml_key leaves the closed primitive set, now ten, because no standard's check.sh called it. The lab starter's TL;DR block now uses the cell markup chrome/lab/tldr.css styles, design/patterns/README.md and design/DESIGN-LANGUAGE.md stop planning a diagram-frame.css when .diagram-frame already ships in the docs chrome, and the design language marks the sidenote pattern as planned, since design/patterns/ holds no sidenote.css.

References

Closes #6 (closed)

Standards affected

design loses one template file. Its check.sh asserts only design-CDN consumption, so no assertion changes, and astro-imports.ts keeps templates/ populated. presentation drops one prose mention of the removed primitive. No check.sh changed and just sync moves no ## Verify block.

Exemption implications

None. No .reference.yaml field changes, and the removed primitive had no call site to exempt.

Test plan

  • just guard passes locally, reporting ten primitives and no violations
  • just check and just check REPO=. pass locally (self-conformance)
  • just build && just agent succeeds (full pre-deploy gate, run as just ship)
  • No standards/<name>/check.sh changed, so no consumer run applies
  • templates/ changed: every class token in the lab starter resolves to a rule in the chrome that starter loads
  • design/ changed: showcase not rendered; the two files touched are prose and no CSS or markup moved

Reviewer checklist

  • Voice is GitLab Inc. neutral (no solo-developer narrative, no decorative essays)
  • No em-dashes in customer-facing prose
  • No filler words ("comprehensive", "robust", "leverage", "seamless")
  • Trailers present (Signed-off-by:, Changelog: if user-visible, AI-Assisted:/AI-Tools: if applicable)
  • CODEOWNERS section matches paths touched
  • If breaking for consumers, CHANGELOG entry calls it out and the schedule is realistic

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