feat(ci): add codex PR review workflow

.github/workflows/codex-review.yml

@@ -0,0 +1,75 @@
+name: Codex PR Review
+
+on:
+  pull_request:
+    types:
+      - opened
+      - synchronize
+      - reopened
+      - ready_for_review
+
+jobs:
+  codex:
+    if: github.event.pull_request.draft == false
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    outputs:
+      final_message: ${{ steps.run_codex.outputs.final-message }}
+    steps:
+      - uses: actions/checkout@v5
+        with:
+          ref: refs/pull/${{ github.event.pull_request.number }}/merge
+
+      - name: Pre-fetch base and head refs for the PR
+        run: |
+          git fetch --no-tags origin \
+            ${{ github.event.pull_request.base.ref }} \
+            +refs/pull/${{ github.event.pull_request.number }}/head
+
+      - name: Run Codex review
+        id: run_codex
+        uses: openai/codex-action@v1
+        with:
+          openai-api-key: ${{ secrets.CODEX_API_KEY }}
+          responses-api-endpoint: ${{ secrets.CODEX_RESPONSES_API_ENDPOINT }}
+          prompt: |
+            This is PR #${{ github.event.pull_request.number }} for ${{ github.repository }}.
+
+            Review only changes from this PR using:
+              git log --oneline ${{ github.event.pull_request.base.sha }}...${{ github.event.pull_request.head.sha }}
+
+            Focus on:
+            - bugs and regressions
+            - security issues
+            - risky edge cases
+            - missing tests where critical
+
+            Keep feedback concise and actionable.
+
+            Pull request title and body:
+            ----
+            ${{ github.event.pull_request.title }}
+            ${{ github.event.pull_request.body }}
+
+  post-feedback:
+    runs-on: ubuntu-latest
+    needs: codex
+    if: needs.codex.outputs.final_message != ''
+    permissions:
+      issues: write
+      pull-requests: write
+    steps:
+      - name: Post Codex feedback to PR
+        uses: actions/github-script@v7
+        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: process.env.CODEX_FINAL_MESSAGE,
+            });