Add envelopes technical specification and integration guide

.cspell.json

@@ -101,6 +101,13 @@
     "hexlify",
     "repoint",
     "repointed",
-    "cutover"
+    "cutover",
+    "autonumber",
+    "dedup",
+    "Linkdrop",
+    "keypair",
+    "typedata",
+    "exfiltrated",
+    "runbook"
   ]
 }

src/envelopes/doc/README.md

@@ -0,0 +1,10 @@
+# Envelopes — Documentation
+
+Bearer-link asset transfer: a sender wraps ETH, ERC-20, ERC-721, or ERC-1155 assets in an on-chain envelope, gets a shareable URL, and anyone holding the URL can claim the contents through the app. Front-run-safe by construction (claim signature commits to the claimer's address).
+
+## Contents
+
+| Document                                                             | Description                                                                                                                          |
+| -------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ |
+| [spec/envelopes-specification.md](spec/envelopes-specification.md)   | Full technical specification (architecture, roles, interfaces, flows, storage, security, testing, ops)                                |
+| [integration-guide.md](integration-guide.md)                          | Operational runbook — TypeScript/ethers.js integration, Cast CLI, sender + app + recipient flows, admin operations, bug-fix rollout  |