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.

docs/02-architecture/archive-nats.md

@@ -54,6 +54,7 @@ If later attach jobs exist for that hash, `receipts` is an array: seal first, th
 | `verae.archive.reply.<correlationId>` | archive on bloom hit | aggregator |
 
 Query payload: `{ correlationId, sha256, tenantId, kinds[] }`.  
+`kinds` may include `tree` for Merkle leaf proofs (hashes sealed only as a bulk summary root).  
 Reply payload: `{ archiveId, sha256, records[] }`.
 
 Bloom miss → no reply. Aggregator timeout → complete with whatever arrived.

docs/02-architecture/modules-and-nats.md

@@ -32,6 +32,9 @@ Zapier cloud **never** connects to NATS. Only middleware workers and archives do
 | request-splitter | `verae-request-splitter` | In middleware | HTTP body / multipart | chain hash; `verae.archive.put` |
 | archive-aggregator | `verae-archive-aggregator` | Worker / in wait | `includeAttached` on wait | `verae.archive.query`; reads `verae.archive.reply.<id>` |
 | archive-worm | `verae-archive-worm` | N copies | `verae.archive.query`, `verae.archive.put` | `verae.archive.reply.<id>` if bloom hits |
+| tree-node | `verae-tree-node` | N copies (WORM role) | `verae.archive.query`, `verae.archive.put` kind `tree` | `verae.archive.reply.<id>` if bloom hits |
+| zapier-simulator | `verae-zapier-simulator` | Local HTTP :3847 | operator browser | in-process replay of all addresses |
+| zapier-user-docs | `zapier-user-docs` | Static | — | catalog `/user-docs/` |
 | verae-chain-client | `verae-chain-client` | Library | — | HTTPS `api.veraetime.net` or MOCK |
 | docs-master | `zapier-docs-master` | Static | — | published on zapier.georgelambert.org |
 

docs/02-architecture/tree-nodes.md

@@ -0,0 +1,44 @@
+# Tree nodes: bulk Merkle summaries vs itemized chain seals
+
+The main Verae chain stores **hash + time + block + certificate**. A Zap that timestamps one document writes that document’s SHA-256 as its own seal.
+
+A **batch** of many documents is different: middleware builds a Merkle tree of the item hashes, seals **only the Merkle root** on the chain, and writes each **leaf proof** to external tree-node NATS archives. A later lookup of a member hash will **miss** on the central chain unless the Zap also queries tree nodes.
+
+```text
+Zapier  HTTPS  zappier-edge  HTTPS  middleware
+                                      |
+                         Merkle root  |  verae.archive.put kind=tree
+                         (chain seal) |  (leaf proof, sharded)
+                                      v
+                               tree-node-east/west/central
+                               bloom miss = silence
+                                      ^
+              hash lookup includeTree |  verae.archive.query
+                                      |  kinds=["tree"]
+                              aggregator merges proof + root seal
+```
+
+## When to use which Zapier search
+
+| Search | Hits |
+|--------|------|
+| Find Timestamp by SHA256 | Hash was registered as its own chain seal |
+| Find Hash (tree nodes + central chain) | Chain first, then `includeTree=true` broadcast |
+
+## Receipt shape for a bulk leaf
+
+```json
+{
+  "sha256": "<leaf>",
+  "exists": true,
+  "itemizedOnMainChain": false,
+  "merkleRoot": "<root sealed on chain>",
+  "proofOk": true,
+  "receipts": [
+    { "kind": "seal", "of": "merkleRoot", "sha256": "<root>", "certificate": "…" },
+    { "kind": "tree-leaf", "archiveId": "tree-node-east", "proof": […], "leafIndex": 1 }
+  ]
+}
+```
+
+Validate this path in the simulator (`packages/verae-zapier-simulator`) before pushing the Zapier app.