chore(deps): bump openai/codex-action from 1.4 to 1.6

Bumps [openai/codex-action](https://github.com/openai/codex-action) from 1.4 to 1.6.
- [Changelog](https://github.com/openai/codex-action/blob/main/CHANGELOG.md)
- [Commits](openai/codex-action@0861694...c25d10f)

---
updated-dependencies:
- dependency-name: openai/codex-action
  dependency-version: '1.6'
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/ai-security-audit.yml

@@ -245,7 +245,7 @@ jobs:
 
       - name: Run AI audit (full repo context)
         id: codex
-        uses: openai/codex-action@086169432f1d2ab2f4057540b1754d550f6a1189 # v1.4
+        uses: openai/codex-action@c25d10f3f498316d4b2496cc4c6dd58057a7b031 # v1.6
         with:
           openai-api-key: ${{ env.OPENAI_API_KEY }}
           prompt-file: ${{ steps.mode.outputs.prompt_file }}