Use WP Codebox v0.12.6 release

[chubes4]

Summary

• Advance the reusable workflow, paired release input, validation checkout, fixtures, and documentation to WP Codebox v0.12.6.
• Validate the tagged producer package and reusable interface, including the controlled native result-file and workflow-result contracts introduced by the release.
• Record WP Codebox run 29296787203 as regression evidence.

How to test

1. Run php tests/validate-docs-agent-bundle.php.
2. Run php tests/validate-external-native-package-sources.php.
3. Run php tests/repair-docs-links-smoke.php.
4. Check out Automattic/wp-codebox at v0.12.6, then run WP_CODEBOX_DIR=/path/to/wp-codebox php tests/validate-wp-codebox-run-agent-task-contract.php.
5. Check out Automattic/agents-api, then run AGENTS_API_DIR=/path/to/agents-api php tests/native-agent-import.php.
6. Run actionlint .github/workflows/*.yml and git diff --check.

AI assistance

• AI assistance: Yes
• Tool(s): OpenAI gpt-5.6-terra via OpenCode
• Used for: Inspected the released WP Codebox contract, updated the consumer release pin and validation coverage, and ran the verification suite.