feat: integrate /codex into /review, /ship, /plan-eng-review + dashboard

/review offers Codex second opinion after completing its own review.
/ship offers Codex review as optional gate before pushing.
/plan-eng-review offers Codex plan critique after scope challenge.
Review Readiness Dashboard shows Codex Review as optional row.

plan-eng-review/SKILL.md

@@ -211,6 +211,27 @@ Before reviewing anything, answer these questions:
 
 If the complexity check triggers (8+ files or 2+ new classes/services), proactively recommend scope reduction via AskUserQuestion — explain what's overbuilt, propose a minimal version that achieves the core goal, and ask whether to reduce or proceed as-is. If the complexity check does not trigger, present your Step 0 findings and proceed directly to Section 1.
 
+### Step 0.5: Codex plan review (optional)
+
+Check if the Codex CLI is available: `which codex 2>/dev/null`
+
+If available, after presenting Step 0 findings, use AskUserQuestion:
+```
+Want an independent Codex (OpenAI) review of this plan before the detailed review?
+A) Yes — let Codex critique the plan independently
+B) No — proceed with the Claude review only
+```
+
+If the user chooses A: read the plan file and run Codex with the plan review persona:
+```bash
+codex exec "You are a brutally honest technical reviewer. Review this plan for: logical gaps and unstated assumptions, missing error handling or edge cases, overcomplexity (is there a simpler approach?), feasibility risks (what could go wrong?), and missing dependencies or sequencing issues. Be direct. Be terse. No compliments. Just the problems." -s read-only
+```
+
+Present the full output under a `CODEX SAYS (plan review):` header. Note any concerns
+that should inform the subsequent engineering review sections.
+
+If Codex is not available, skip silently.
+
 Always work through the full interactive review: one section at a time (Architecture → Code Quality → Tests → Performance) with at most 8 top issues per section.
 
 **Critical: Once the user accepts or rejects a scope reduction recommendation, commit fully.** Do not re-argue for smaller scope during later review sections. Do not silently reduce scope or skip planned components.
@@ -384,7 +405,7 @@ echo "---CONFIG---"
 ~/.claude/skills/gstack/bin/gstack-config get skip_eng_review 2>/dev/null || echo "false"
 ```
 
-Parse the output. Find the most recent entry for each skill (plan-ceo-review, plan-eng-review, plan-design-review, design-review-lite). Ignore entries with timestamps older than 7 days. For Design Review, show whichever is more recent between `plan-design-review` (full visual audit) and `design-review-lite` (code-level check). Append "(FULL)" or "(LITE)" to the status to distinguish. Display:
+Parse the output. Find the most recent entry for each skill (plan-ceo-review, plan-eng-review, plan-design-review, design-review-lite, codex-review). Ignore entries with timestamps older than 7 days. For Design Review, show whichever is more recent between `plan-design-review` (full visual audit) and `design-review-lite` (code-level check). Append "(FULL)" or "(LITE)" to the status to distinguish. Display:
 
 ```
 +====================================================================+
@@ -395,6 +416,7 @@ Parse the output. Find the most recent entry for each skill (plan-ceo-review, pl
 | Eng Review      |  1   | 2026-03-16 15:00    | CLEAR     | YES      |
 | CEO Review      |  0   | —                   | —         | no       |
 | Design Review   |  0   | —                   | —         | no       |
+| Codex Review    |  0   | —                   | —         | no       |
 +--------------------------------------------------------------------+
 | VERDICT: CLEARED — Eng Review passed                                |
 +====================================================================+
@@ -404,11 +426,12 @@ Parse the output. Find the most recent entry for each skill (plan-ceo-review, pl
 - **Eng Review (required by default):** The only review that gates shipping. Covers architecture, code quality, tests, performance. Can be disabled globally with \`gstack-config set skip_eng_review true\` (the "don't bother me" setting).
 - **CEO Review (optional):** Use your judgment. Recommend it for big product/business changes, new user-facing features, or scope decisions. Skip for bug fixes, refactors, infra, and cleanup.
 - **Design Review (optional):** Use your judgment. Recommend it for UI/UX changes. Skip for backend-only, infra, or prompt-only changes.
+- **Codex Review (optional):** Independent second opinion from OpenAI Codex CLI. Shows pass/fail gate. Recommend for critical code changes where a second AI perspective adds value. Skip when Codex CLI is not installed.
 
 **Verdict logic:**
 - **CLEARED**: Eng Review has >= 1 entry within 7 days with status "clean" (or \`skip_eng_review\` is \`true\`)
 - **NOT CLEARED**: Eng Review missing, stale (>7 days), or has open issues
-- CEO and Design reviews are shown for context but never block shipping
+- CEO, Design, and Codex reviews are shown for context but never block shipping
 - If \`skip_eng_review\` config is \`true\`, Eng Review shows "SKIPPED (global)" and verdict is CLEARED
 
 ## Unresolved decisions

plan-eng-review/SKILL.md.tmpl

@@ -82,6 +82,27 @@ Before reviewing anything, answer these questions:
 
 If the complexity check triggers (8+ files or 2+ new classes/services), proactively recommend scope reduction via AskUserQuestion — explain what's overbuilt, propose a minimal version that achieves the core goal, and ask whether to reduce or proceed as-is. If the complexity check does not trigger, present your Step 0 findings and proceed directly to Section 1.
 
+### Step 0.5: Codex plan review (optional)
+
+Check if the Codex CLI is available: `which codex 2>/dev/null`
+
+If available, after presenting Step 0 findings, use AskUserQuestion:
+```
+Want an independent Codex (OpenAI) review of this plan before the detailed review?
+A) Yes — let Codex critique the plan independently
+B) No — proceed with the Claude review only
+```
+
+If the user chooses A: read the plan file and run Codex with the plan review persona:
+```bash
+codex exec "You are a brutally honest technical reviewer. Review this plan for: logical gaps and unstated assumptions, missing error handling or edge cases, overcomplexity (is there a simpler approach?), feasibility risks (what could go wrong?), and missing dependencies or sequencing issues. Be direct. Be terse. No compliments. Just the problems." -s read-only
+```
+
+Present the full output under a `CODEX SAYS (plan review):` header. Note any concerns
+that should inform the subsequent engineering review sections.
+
+If Codex is not available, skip silently.
+
 Always work through the full interactive review: one section at a time (Architecture → Code Quality → Tests → Performance) with at most 8 top issues per section.
 
 **Critical: Once the user accepts or rejects a scope reduction recommendation, commit fully.** Do not re-argue for smaller scope during later review sections. Do not silently reduce scope or skip planned components.