ci(codex): add advisory Codex PR review (VGTR-2539)

.github/codex-review-prompt.md

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+# Code Review Guidelines
+
+valigatorHealthCheck is a Bash system health-check and diagnostics toolkit for Valigator's Linux validator servers, with an Ansible deployment playbook.
+
+Review ONLY the changes in this pull request: the diff between the base branch
+and the pull request head (`git diff origin/<base>...HEAD`). Do not comment on
+unchanged code.
+
+Read enough of the repository to review against its real conventions (the
+README, any CLAUDE.md, and the files the change touches) before commenting.
+
+## What to look for
+
+- Bugs and logic errors: wrong conditions, unhandled failures, broken paths or
+  references, behaviour that does not match the change's evident intent.
+- Security: secrets, tokens or keys committed in the diff; command injection or
+  unquoted variables in shell; unsafe use of `eval`, `sudo` or `rm`; disabled
+  TLS verification; overly broad permissions in workflow files.
+- Operational risk: changes that could break a production host, service or
+  scheduled job, or remove a safety check.
+
+Do not comment on style, formatting or wording.
+
+## Output format
+
+List each finding on its own line as `Severity: path:line: issue and suggested
+fix`, where Severity is Critical, High, Medium or Low. If there are no findings,
+reply with the single line `No findings.`

.github/workflows/codex-review.yml

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+# Codex PR Review: an independent AI review of every pull request, posted as a
+# PR comment. Advisory: it does not fail the check on findings. Added under
+# VGTR-2539 so each change to this repository carries a recorded independent
+# review (SOC 2 CC8.1 change-review control). Same pattern as the Codex review
+# in noise, gatorStats and rpc-proxy. Third-party actions pinned to commit SHAs.
+#
+# Secret exposure (accepted risk): pull_request runs the workflow from the PR
+# merge commit, so a same-repository PR could edit this file to read
+# OPENAI_API_KEY. That grants nothing new: anyone with write access can already
+# read repository secrets by pushing a workflow on any branch. Fork PRs are
+# excluded by the head.repo guard, and the only user accounts with write access
+# are the two principals. The control is write-access governance, not this
+# workflow.
+name: Codex PR Review
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened, ready_for_review]
+
+concurrency:
+  group: codex-review-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+jobs:
+  codex:
+    if: >-
+      github.actor != 'dependabot[bot]'
+      && github.event.pull_request.head.repo.full_name == github.repository
+      && github.event.pull_request.draft == false
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    outputs:
+      final_message: ${{ steps.run_codex.outputs.final-message }}
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          ref: refs/pull/${{ github.event.pull_request.number }}/merge
+          fetch-depth: 0
+
+      - name: Pre-fetch base and head refs
+        env:
+          BASE_REF: ${{ github.event.pull_request.base.ref }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+        run: |
+          git fetch --no-tags origin \
+            "$BASE_REF" \
+            "+refs/pull/${PR_NUMBER}/head"
+
+      - name: Run Codex
+        id: run_codex
+        uses: openai/codex-action@52fe01ec70a42f454c9d2ebd47598f9fd6893d56 # v1.11
+        with:
+          openai-api-key: ${{ secrets.OPENAI_API_KEY }}
+          model: gpt-6-luna
+          prompt-file: .github/codex-review-prompt.md
+          codex-home: ${{ runner.temp }}/codex-home
+
+  post_feedback:
+    runs-on: ubuntu-latest
+    needs: codex
+    if: needs.codex.outputs.final_message != ''
+    # Both permissions are kept on purpose. With issues: write alone the PR
+    # comment returned 403 "Resource not accessible by integration" (verified
+    # 2026-10-28); this pair is the configuration verified to post the comment.
+    # The job runs no PR code and holds no other secret.
+    permissions:
+      issues: write
+      pull-requests: write
+    steps:
+      - name: Post review comment
+        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
+        env:
+          CODEX_FINAL_MESSAGE: ${{ needs.codex.outputs.final_message }}
+        with:
+          github-token: ${{ github.token }}
+          script: |
+            await github.rest.issues.createComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.payload.pull_request.number,
+              body: `## 🤖 Codex Review\n\n${process.env.CODEX_FINAL_MESSAGE}`,
+            });