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-contracts/src/pairing/enroll.ts

@@ -0,0 +1,50 @@
+/**
+ * §4.5 Pairing / enrollment shapes. P3 issues pairing codes and returns EnrollResult at BIND;
+ * P2 redeems. `hostContentSecret` (FIX 3) is wrapped to the agent's enrolled Ed25519 identity
+ * by P3 and unwrapped locally by P2 (private key never leaves the host, INV4).
+ */
+import { z } from 'zod'
+
+/**
+ * Result of a successful `POST /enroll` (§4.5). `hostContentSecret` is the wrapped-to-agent
+ * input to §4.4 `deriveContentKey`; NEVER logged, NEVER sent to the relay.
+ */
+export interface EnrollResult {
+  readonly hostId: string
+  readonly subdomain: string
+  readonly cert: string
+  readonly caChain: string
+  readonly hostContentSecret: Uint8Array // FIX 3 — wrapped to agent_pubkey by P3 at BIND
+}
+
+export const EnrollResultSchema = z
+  .object({
+    hostId: z.string().uuid(),
+    subdomain: z.string().min(1),
+    cert: z.string().min(1),
+    caChain: z.string().min(1),
+    hostContentSecret: z.instanceof(Uint8Array),
+  })
+  .strict()
+  .readonly()
+
+/**
+ * pairing_codes row (§4.2/§4.5). Only the HASH of the single-use code is stored (INV5);
+ * a non-null `redeemedAt` marks it spent (single-use, atomic compare-and-set at redeem).
+ */
+export interface PairingCodeRecord {
+  readonly codeHash: string
+  readonly accountId: string
+  readonly expiresAt: string
+  readonly redeemedAt: string | null
+}
+
+export const PairingCodeRecordSchema = z
+  .object({
+    codeHash: z.string().min(1),
+    accountId: z.string().uuid(),
+    expiresAt: z.string().datetime({ offset: true }),
+    redeemedAt: z.string().datetime({ offset: true }).nullable(),
+  })
+  .strict()
+  .readonly()