Add Zapier interface simulator, tree-node Merkle lookups, and user docs

In-process trace console validates hops, faults, recoveries, and
suggested changes before zapier-platform push. User guide covers
signup through central-chain and bulk-summary tree-node hash lookup.

packages/zapier-user-docs/02-signup-zappier-portal.md

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+# 2. Sign up for a Verae / zappier account
+
+You need an API key **before** you can connect Zapier.
+
+1. Open the customer portal (`/portal` on the zappier host your operator gave you).
+2. Choose **Create an account**.
+3. Enter name, email, and a password of at least 8 characters.
+4. You start on the **Free** plan and receive an **API key immediately**.
+5. Copy the key. It is sent as `x-api-key` on every Zapier request.
+
+If your company already created an account (you received a key by email), sign up with the **same email**. The existing plan and key are kept; your password is attached to that account.
+
+## After signup
+
+- **Dashboard** — usage this month, included credit, billable overage, prepaid balance.
+- **API & pricing** — live rate card (free / fixed / variable per operation, including batch).
+- **Invoices** — draft / issued / paid.
+- **Billing** — reload $1–$10,000; prepaid is drawn down automatically.
+- **Security** — optional 2FA.
+
+Regenerating the API key **invalidates the old one immediately**. Update the Zapier authentication field or every Zap step will 401.
+
+Simulator: action **Sign up (zappier portal)** then **Connect Zapier app**.