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/03-connect-zapier.md

@@ -0,0 +1,19 @@
+# 3. Connect the Zapier app
+
+1. Sign in at [zapier.com](https://zapier.com) (or your Zapier workspace).
+2. Create a Zap → add **Verae Time** (or **Verae Activate** while the full app is in private invite).
+3. When Zapier asks for authentication, paste:
+   - **API key** from the zappier portal.
+   - **API base URL** if the operator asked you to (hosted edge). Leave blank only for local-mock Activate steps that do not hit the chain.
+4. Click **Test**. Zapier calls zappier-edge over HTTPS (`whoami` / a cheap GET). You should see your email and plan. A 401 means the key was regenerated or mistyped.
+
+You do **not** enter NATS URLs, Verae JWT, or `api.veraetime.net` credentials. Those stay on middleware.
+
+## Plans
+
+| Plan | Typical access |
+|------|----------------|
+| Free | Single timestamp, lookup, Add Numbers / Echo / SHA256 helpers |
+| Paid | Batch timestamps, wait-for-certificate, attached metadata, tree-node lookup |
+
+A 403 `PLAN_UPGRADE_REQUIRED` means that Zap step is paid-only. A 402 means you exhausted included credit — reload in the portal (the error should include an upgrade URL).