Harden browser recipe execution

[chubes4]

Summary

• Harden browser recipe execution by writing task payloads through the browser operation path and parsing Playground client.run() byte/text response shapes with bounded diagnostics.
• Run browser recipes as internal REST runner requests, preserve provider/model context for agents/chat, import Data Machine bundles through scoped authenticated context, and keep browser session ids out of transcript session ids.
• Keep fixed preview-port sessions same-origin by using the local preview URL as siteUrl and preserving the browser-visible host through the proxy.

Testing

• npm install (refresh workspace links; install-triggered build passed)
• npm run package:wordpress-plugin
• npm run browser-runtime-operation-smoke
• npm run preview-port-smoke
• php tests/smoke-wordpress-plugin.php

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (openai/gpt-5.5)
• Used for: Debugging the browser recipe/live-eval failure path, drafting the patch, resolving the rebase conflict, and running targeted verification. Chris remains responsible for review and merge.