fix(codex): resolve review resources via runtime root

[uncfreak1255-code]

Summary

• rewrite Codex review-resource references to $GSTACK_ROOT/review
• declare all four review runtime resources, including design and Greptile checklists
• regenerate the Codex /ship golden fixture and update generator regressions
• execute the generated preamble in temporary consumer repos to prove global and repo-local installations both resolve every review resource

Verification

• bun test test/gen-skill-docs.test.ts test/host-config.test.ts test/setup-windows-fallback.test.ts — 488 passed
• bun run build — passed
• Codex Autoreview (--mode local) — clean, no actionable findings
• generated-path scan — no .agents/skills/gstack/review/... review-resource references remain
• bun run eval:select — 0/181 E2E and 0/28 LLM-judge tests selected

Known base/toolchain exceptions

• bun run test:windows reaches an untouched origin/main assertion mismatch: test/helpers/observability.test.ts expects six /* non-fatal */ markers while origin/main:test/helpers/session-runner.ts contains five. This branch has no diff in either file.
• bun run test:evals selected no model tests and spent $0.00, but an always-loaded Swift fixture test cannot import XCTest because this machine has Command Line Tools only, not full Xcode. The Swift test and fixture are unchanged from origin/main.

These exceptions are documented rather than patched here to keep the change scoped to Codex resource resolution.

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