feat(relay): rendezvous-relay service — 7 packages + plans (contracts/transport/agent/control-plane/e2e/auth/web)

Multi-tenant reverse-tunnel service ("ngrok for Claude Code" with E2E): a
host-agent dials OUT to an operator-run relay; external devices reach the host
THROUGH the relay, routed by per-tenant subdomain, forwarding ciphertext only
(the relay never sees plaintext). Lets a customer reach their own self-hosted
web-terminal from anywhere with zero networking setup.

Packages — all tsc-strict + vitest green (656 tests), cross-package integration verified:
- relay-contracts: frozen shared contracts (mux frame codec, data model,
  capability token, E2E envelope, pairing) — the src/types.ts analog
- term-relay:   native WS mux + stateless data plane (subdomain routing, ciphertext forward)
- agent:        host-agent (pairing, per-host Ed25519 + mTLS dial-out, forwards to 127.0.0.1:3000)
- control-plane: accounts/hosts registry, pairing-code flow, routing table, provisioning
- relay-e2e:    browser<->agent E2E (X25519 ECDH through relay, AEAD, anti-replay, recoverable replay key)
- relay-auth:   Passkey/WebAuthn, capability tokens, per-host certs, deny-by-default tenant isolation
- relay-web:    browser login + Web Crypto E2E + client-side preview rendering

Security invariants INV1-15 enforced; cross-tenant isolation CI tripwire live
(.github/workflows/relay-tripwire.yml). Design + implementation-level plans in
docs/PLAN_RELAY_*.md and docs/EXPLORE_RELAY_SERVICE.md.

NOTE: generated autonomously per the reviewed plans. The security-critical
packages (relay-e2e, relay-auth) REQUIRE expert security audit before any real
deployment — passing tests prove self-consistency, not resistance to attackers.
Base app (src/, public/) unchanged; concurrent desktop work left uncommitted.

relay-e2e/package.json

@@ -0,0 +1,34 @@
+{
+  "name": "relay-e2e",
+  "version": "0.0.0",
+  "private": true,
+  "type": "module",
+  "description": "P4 — browser<->agent end-to-end encryption core (ciphertext-shuttle) for the rendezvous-relay service. Isomorphic (browser + Node >=20) AEAD/ECDH/HKDF crypto implementing the FROZEN relay-contracts §4.4 signatures (sealFrame/openFrame/createE2ESession/buildClientHandshake/deriveContentKey/...). No ws/pg/DOM-runtime/xterm imports. See docs/PLAN_RELAY_E2E.md.",
+  "engines": {
+    "node": ">=20"
+  },
+  "main": "src/index.ts",
+  "types": "src/index.ts",
+  "exports": {
+    ".": "./src/index.ts"
+  },
+  "scripts": {
+    "typecheck": "tsc --noEmit",
+    "build": "tsc --noEmit",
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "test:coverage": "vitest run --coverage"
+  },
+  "dependencies": {
+    "@noble/ciphers": "^1.2.1",
+    "@noble/curves": "^1.8.1",
+    "@noble/hashes": "^1.7.1",
+    "relay-contracts": "file:../relay-contracts",
+    "zod": "^3.23.8"
+  },
+  "devDependencies": {
+    "@types/node": "^25.9.3",
+    "typescript": "^6.0.3",
+    "vitest": "^4.1.9"
+  }
+}