Add browser runtime replay package export

[chubes4]

Summary

• Add a wordpress.browser-export-replay-package command that exports a nested browser Playground WordPress site as the existing replay-package artifact shape.
• Include blueprint.zip, blueprint.after.json, files/runtime-snapshot.json, notes, and manifest refs in artifact collection.
• Avoid stack overflows in artifact collection by not digesting full embedded snapshot payloads for reference manifests.

Verification

• npm run build
• Studio Web Workflow Bench exercised this command via scripts/workflow-bench.mjs run --matrix website-generation-studio-web --run-id nested-replay-r11 ....

Current blocker

• The command successfully creates a full replay package, but Studio Web still needs to call it from the browser session that owns the already-materialized generated project target. Fresh command sessions can re-open a default/starter nested target.

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (GPT-5.5)
• Used for: Drafted and tested the browser replay export command and artifact collection changes; Chris remains responsible for review and final validation.