refactor: just build + retire the scaffold script for an SSOT-map on-ramp

What and why

The simplification that came out of consuming the reference as a greenfield project. Reference's value is the source of truth (the standards, the just check oracle, the templates as exemplars) plus a map an agent or person follows to build a conformant project, not a placeholder-stamping script or a heavy preview-rendering apparatus.

Stacked on !18 (merged). Targets andunn-reference-scaffold-fix; retarget to main once !18 (merged) merges.

The changes

Area	Change
make → just	Makefile becomes a behavior-identical justfile. Every reference to the repo's own targets (CI, scripts, docs, templates) moves to just. The make-style trailing KEY=VALUE CLI is preserved.
Retire new-project.sh	The stamping script + new-project recipe are removed. Greenfield projects were hand-assembled by an agent anyway; the script's failure modes (placeholder substitution, perl/git deps, born-broken output) are friction the SSOT model does not have.
Retire preview-capture	The build-time template-preview-capture subsystem (capture-template-previews.mjs, the CI job, the justfile recipe) is removed. It depended on the scaffold and pulled in the heavy ci-latex + Playwright + tectonic toolchain for cosmetic screenshots. Template pages already degrade to a prose note when the PNGs are absent.
SSOT-map on-ramp	README ## Start a new project: read the standards (just list + SKILL.md + llms-full.txt), copy a template, fill real values, run just check. Same steps for an agent or a person.
just check advisory	self-conformance CI job is allow_failure: true: a reminder of what differs from the standards, not a gate. The structural validate job stays hard.
Fix vale	The vale@v3.3.0 component renders an empty ci-tools: image tag ($[[ component.version ]] interpolation bug, fixed upstream at catalog v4.0.1). Pin the image to the intended tag so the linter runs.

Validation

• SSOT-map workflow proven with no script: copy templates/docs/, fill placeholders, just check REPO=. → 17 standards, 0 failed.
• just --list / check / validate / list / version / check-one / guard behave as the prior Makefile did. apk add just confirmed on the alpine CI jobs.

Draft for review.