refactor(ship): carve into skeleton + on-demand sections (Claude) (T9)

ship/SKILL.md drops 167KB → 68.7KB (~59% of the always-loaded skill) by moving
8 prose-heavy steps into ship/sections/*.md, read on demand:
tests, test-coverage, plan-completion, review-army, greptile, adversarial,
changelog, pr-body. Step 12's version logic now calls the tested
gstack-version-bump CLI instead of inline bash.

Claude-first (S2): {{SECTION:id}} emits a STOP-Read pointer on Claude (skeleton +
generated section files) and INLINES the content on every other host, so external
hosts keep the full monolith — verified factory at 162KB with no sections dir.
{{SECTION_INDEX:ship}} renders the situation→section table from the PASSIVE
manifest (CM2 / v2_PLAN.md:663); required-reads live only in test fixtures.
Multi-pass resolve expands inlined sections' own resolvers.

Parity: ship invariant flipped to sectioned (union content checks + maxSkeletonBytes
asserts the shrink). Carve-fallout fixed across gen-skill-docs/skill-validation/
golden/plan-completion/#1539/size-budget tests via skeleton+sections union reads.
Free suite green except the pre-existing investigate parity drift.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

test/helpers/parity-harness.ts

@@ -207,7 +207,13 @@ export const PARITY_INVARIANTS: ParityInvariant[] = [
     minBytes: 30_000,
   },
   {
+    // Carved (v2 plan T9): skeleton SKILL.md + sections/*.md. Content checks run
+    // against the union (relocated phrases still count); size floors run against
+    // the union (total behavior preserved); maxSkeletonBytes asserts the
+    // always-loaded skeleton actually shrank from the ~167KB monolith.
     skill: 'ship',
+    sectioned: true,
+    maxSkeletonBytes: 90_000,
     mustContain: [
       'VERSION',
       'CHANGELOG',
@@ -217,7 +223,7 @@ export const PARITY_INVARIANTS: ParityInvariant[] = [
     ],
     mustHaveHeadings: ['## Preamble', '## When to invoke'],
     maxSizeRatio: 1.05,
-    minBytes: 80_000,
+    minBytes: 120_000,
   },
   {
     skill: 'plan-ceo-review',