fix: support wp-cli bench workloads

[chubes4]

Summary

• Route wordpress.bench workload steps of type: "wp-cli" through the existing runtime WP-CLI bridge instead of trying to load WP-CLI inside the active bench PHP process.
• Auto-grant wordpress.wp-cli in recipe policy when a wordpress.bench recipe includes configured WP-CLI workload steps.
• Extend the bench smoke to prove a WP-CLI workload step can update WordPress state observed by a later PHP step.

Testing

• npm run build
• npm run recipe-bench-smoke
• npm run recipe-dry-run-smoke
• npm run discovery-command-smoke
• git diff --check

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (openai/gpt-5.5)
• Used for: Diagnosed the wordpress.bench WP-CLI workload crash, drafted the bridge-based runtime/policy changes, and ran focused local verification. Chris remains responsible for review and merge.