feat: design review lite in /review and /ship + gstack-diff-scope (v0.6.3) (#142)

* feat: gstack-diff-scope helper + design review checklist

bin/gstack-diff-scope categorizes branch changes into SCOPE_FRONTEND,
SCOPE_BACKEND, SCOPE_PROMPTS, SCOPE_TESTS, SCOPE_DOCS, SCOPE_CONFIG.

review/design-checklist.md is a 20-item code-level checklist with
HIGH/MEDIUM/LOW confidence tags for detecting design anti-patterns
from source code.

* feat: integrate design review lite into /review and /ship

Add generateDesignReviewLite() resolver, insert {{DESIGN_REVIEW_LITE}}
partial in review Step 4.5 and ship Step 3.5. Update dashboard to
recognize design-review-lite entries. Ship pre-flight uses
gstack-diff-scope for smarter design review recommendations.

* test: E2E eval for design review lite detection

Planted CSS/HTML fixtures with 7 design anti-patterns. E2E test
verifies /review catches >= 4 of 7 (Papyrus font, 14px body text,
outline:none, !important, purple gradient, generic hero copy,
3-column feature grid).

* chore: bump version and changelog (v0.6.3.0)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>