feat(design): write/read DESIGN.md in the open spec; persisted format choice

gstack's design skills now write DESIGN.md in the open DESIGN.md format and
read tokens from it. {{DESIGN_MD_CHECK}} renders the format check through
bin/gstack-design-md.ts: design-consultation's Phase 0 settles the format once
(spec → update tokens in the front matter; legacy without a marker → one
AskUserQuestion: convert with a .legacy.bak, keep the legacy file, or start
fresh; the answer is written into the file as the format marker so no skill
asks again; a marker already present is obeyed silently; unknown → prose;
missing → Phase 6 writes one). Phase 6's template is the spec form: YAML front
matter with name, description, and exactly the five token groups (colors,
typography.display/body/label/mono with fontFeature: tnum on mono, rounded,
spacing, components with {path} references), then Overview (Creative North
Star, product context, mode per surface, references, key characteristics),
Colors (opening with the Restrained / Committed / Full palette / Drenched
strategy), Typography, Layout, Elevation & Depth, Shapes, Components, Do's and
Don'ts, plus gstack's Motion and Decisions Log as extras; the template ends
with a check that the file parses as `spec`.

design-review runs the `:calibrate` form in Setup: a spec file's flat tokens
are the calibration source (a value present in the tokens is never a finding),
the marker is respected, and conversion is never offered there; its DESIGN.md
export writes the spec form. design-html's token extraction writes the spec
form and respects an existing choice. review/design-checklist.md category 5 and
ship's review-lite step 1 name `gstack-design-md tokens` as the calibration
source; plan-design-review Pass 5 cites tokens by path when front matter
exists.

The contract owns the bin's DESIGN_MD_MARKER / REASON / WRITTEN / BACKUP
lines; the contract test's pending list closes. Carve guard: design-
consultation skeleton 66,500 → 67,500 (measured 67,014; +1,508 B against the
1.5 KB cap). Codex and Factory ship goldens refreshed (review-lite step 1).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

plan-design-review/sections/review-sections.md

@@ -184,7 +184,7 @@ If visual mockups were generated in Step 0.5, evaluate them against the AI slop
 
 ### Pass 5: Design System Alignment
 Rate 0-10: Does the plan align with DESIGN.md?
-FIX TO 10: If DESIGN.md exists, annotate with specific tokens/components. If no DESIGN.md, flag the gap and recommend `/design-consultation`.
+FIX TO 10: If DESIGN.md exists, annotate with specific tokens/components; when it has YAML front matter (the open DESIGN.md format), cite tokens by path (`{colors.primary}`, `{rounded.md}`) so the plan and the file share one vocabulary. If no DESIGN.md, flag the gap and recommend `/design-consultation`.
 Flag any new component — does it fit the existing vocabulary?
 **STOP.** AskUserQuestion once per issue. Do NOT batch. Recommend + WHY.
 

plan-design-review/sections/review-sections.md.tmpl

@@ -49,7 +49,7 @@ If visual mockups were generated in Step 0.5, evaluate them against the AI slop
 
 ### Pass 5: Design System Alignment
 Rate 0-10: Does the plan align with DESIGN.md?
-FIX TO 10: If DESIGN.md exists, annotate with specific tokens/components. If no DESIGN.md, flag the gap and recommend `/design-consultation`.
+FIX TO 10: If DESIGN.md exists, annotate with specific tokens/components; when it has YAML front matter (the open DESIGN.md format), cite tokens by path (`{colors.primary}`, `{rounded.md}`) so the plan and the file share one vocabulary. If no DESIGN.md, flag the gap and recommend `/design-consultation`.
 Flag any new component — does it fit the existing vocabulary?
 **STOP.** AskUserQuestion once per issue. Do NOT batch. Recommend + WHY.