[codex] Fix ship qa-only path for Codex host

[spacegeologist]

Summary

Fixes the generated Codex-host /ship skill so plan verification loads /qa-only from the Codex gstack skill layout.

Related context

This is part of the same Codex-host compatibility cleanup series as the earlier Codex adaptation PR. The prior PR handled Codex-specific auth/preflight behavior; this PR addresses a separate generated-skill path issue in /ship plan verification.

Root cause

/ship plan verification was still emitting the Claude-specific ${CLAUDE_SKILL_DIR}/../qa-only/SKILL.md lookup. In Codex installs, generated skills are prefixed siblings like gstack-qa-only, and the runtime preamble exposes $GSTACK_ROOT, so the Claude-only path cannot resolve.

What changed

• Add a Codex host path rewrite for ${CLAUDE_SKILL_DIR}/../qa-only/SKILL.md.
• Keep Claude-host output unchanged.
• Add a Codex generation regression test for gstack-ship.

CI note

The earlier draft head touched scripts/resolvers/review.ts, which caused review/design eval shards to run on a fork PR without API secrets and fail with error_api. The current head avoids that shared resolver touch; the rerun shows all E2E/LLM eval jobs passing, including the previously failing e2e-design and e2e-review shards.

The only remaining red job is report, which fails while posting the PR comment with GraphQL: Resource not accessible by integration (addComment). That is the known fork PR comment-permission limitation rather than a test failure.

Validation

• bun test test/gen-skill-docs.test.ts — 390 pass
• bun test test/codex-hardening.test.ts — 29 pass
• bun run gen:skill-docs --host codex --dry-run — all Codex skills FRESH
• bun run eval:select --base origin/main — E2E 0/165, LLM-judge 0/28 affected
• GitHub CI on 67af98f: Skill Docs Freshness, Workflow Lint, Windows Free Tests, and all E2E/LLM eval shards pass
• git diff --check