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.

agent/test/fixtures/fakes.ts

@@ -0,0 +1,63 @@
+import type { WsLike, TimerLike } from '../../src/transport/seams.js'
+
+/** In-memory WsLike double: records sent frames, lets tests emit inbound events. */
+export class FakeWs implements WsLike {
+  readonly sent: Uint8Array[] = []
+  closed = false
+  private readonly listeners = new Map<string, Array<(...a: unknown[]) => void>>()
+
+  send(d: Uint8Array): void {
+    this.sent.push(d)
+  }
+  on(ev: 'message' | 'close' | 'error', cb: (...a: unknown[]) => void): void {
+    const arr = this.listeners.get(ev) ?? []
+    arr.push(cb)
+    this.listeners.set(ev, arr)
+  }
+  close(): void {
+    this.closed = true
+    this.emit('close')
+  }
+  emit(ev: string, ...args: unknown[]): void {
+    for (const cb of this.listeners.get(ev) ?? []) cb(...args)
+  }
+  emitMessage(bytes: Uint8Array): void {
+    this.emit('message', bytes)
+  }
+}
+
+/** Deterministic controllable timer for heartbeat/rotation tests. */
+export class FakeTimer implements TimerLike {
+  private seq = 0
+  private readonly timeouts = new Map<number, { cb: () => void; ms: number }>()
+  private readonly intervals = new Map<number, { cb: () => void; ms: number }>()
+
+  setTimeout(cb: () => void, ms: number): unknown {
+    const id = this.seq++
+    this.timeouts.set(id, { cb, ms })
+    return id
+  }
+  clearTimeout(handle: unknown): void {
+    this.timeouts.delete(handle as number)
+  }
+  setInterval(cb: () => void, ms: number): unknown {
+    const id = this.seq++
+    this.intervals.set(id, { cb, ms })
+    return id
+  }
+  clearInterval(handle: unknown): void {
+    this.intervals.delete(handle as number)
+  }
+  /** Fire every armed timeout whose delay is ≤ ms (single shot) and every interval once. */
+  advance(ms: number): void {
+    for (const [id, t] of [...this.timeouts]) {
+      if (t.ms <= ms) {
+        this.timeouts.delete(id)
+        t.cb()
+      }
+    }
+    for (const t of [...this.intervals.values()]) {
+      if (t.ms <= ms) t.cb()
+    }
+  }
+}