Add artifact review workflow

[chubes4]

Summary

• Adds a plugin-level wp-codebox/review-artifact ability for normalized artifact review decisions.
• Preserves generic approve/reject/request-changes decision payloads, provenance, message shape, and separate review audit records.
• Keeps product-specific consequences behind adapters: approvals fall through to the existing approved-artifact apply adapter, while non-approval decisions use the generic review decision hook/result path.

Tests

• npm run wordpress-plugin-smoke
• npm run browser-review-bridge-smoke

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (openai/gpt-5.5)
• Used for: Implementation and tests for the plugin-level artifact review workflow; Chris remains responsible for review and merge decisions.