Day 5 — MCP-spun form (via JSON-RPC)
Form template now folded into web_artifact_spin_up
One JSON-RPC call did everything: template copy, forms-handler registration via /admin/pages (or PUT-update on 409), signing-key inject into form.json, out-of-tree build, wrangler create+deploy, verify.
Architecture B is now as friction-free as Architecture A. Day 5 #1 acceptance criterion met.