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-web/test/add-machine.test.ts

@@ -0,0 +1,106 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import { mountAddMachine } from '../src/add-machine'
+import { ApiError } from '../src/errors'
+import type { ApiClient } from '../src/api-client'
+import type { HostRecord } from '../src/api-schemas'
+
+function host(subdomain: string, status: HostRecord['status'] = 'online'): HostRecord {
+  return {
+    hostId: `id-${subdomain}`,
+    accountId: 'acc',
+    subdomain,
+    agentPubkey: new Uint8Array([1]),
+    enrollFpr: `fpr-${subdomain}`,
+    status,
+    lastSeen: '2026-01-01T00:00:00Z',
+    createdAt: '2026-01-01T00:00:00Z',
+    revokedAt: null,
+  }
+}
+
+function fakeApi(over: Partial<ApiClient>): ApiClient {
+  return {
+    listHosts: vi.fn(async () => []),
+    getHost: vi.fn(),
+    requestPairingCode: vi.fn(),
+    hostStatus: vi.fn(),
+    issueCapabilityToken: vi.fn(),
+    ...over,
+  } as unknown as ApiClient
+}
+
+const flush = () => new Promise((r) => setTimeout(r, 0))
+const tick = (ms: number) => new Promise((r) => setTimeout(r, ms))
+
+describe('mountAddMachine (T6)', () => {
+  let root: HTMLElement
+  beforeEach(() => {
+    root = document.createElement('div')
+    document.body.append(root)
+  })
+
+  it('happy path: shows npx command, detects a newly online host, fires onPaired once', async () => {
+    let call = 0
+    const listHosts = vi.fn(async () => (call++ === 0 ? [] : [host('newbox')]))
+    const requestPairingCode = vi.fn(async () => ({ code: 'ABCD-1234', expiresAt: futureIso() }))
+    const onPaired = vi.fn()
+    const api = fakeApi({ listHosts, requestPairingCode })
+    const add = mountAddMachine(root, api, { pollMs: 5, onPaired })
+
+    await add.start()
+    await flush()
+    await flush()
+    await flush()
+
+    expect(root.querySelector('.pair-command')?.textContent).toBe(
+      'npx web-terminal-agent pair ABCD-1234',
+    )
+    expect(onPaired).toHaveBeenCalledExactlyOnceWith('id-newbox')
+    add.dispose()
+  })
+
+  it('expired code: after expiresAt it shows "expired", clears the code, and stops polling', async () => {
+    let t = 1_000_000
+    const requestPairingCode = vi.fn(async () => ({ code: 'EXP-0001', expiresAt: new Date(t + 50).toISOString() }))
+    const listHosts = vi.fn(async () => [])
+    const api = fakeApi({ listHosts, requestPairingCode })
+    const add = mountAddMachine(root, api, { pollMs: 5, now: () => t })
+
+    await add.start()
+    t += 100 // advance past expiry
+    await tick(25) // let the poll interval fire and catch expiry
+
+    expect(root.querySelector('.pair-status')?.textContent).toContain('expired')
+    expect(root.querySelector('.pair-command')?.textContent).toBe('')
+    const callsAtExpiry = listHosts.mock.calls.length
+    await tick(25)
+    expect(listHosts.mock.calls.length).toBe(callsAtExpiry) // polling stopped
+    add.dispose()
+  })
+
+  it('a requestPairingCode failure surfaces an error and does not start an infinite poll', async () => {
+    const requestPairingCode = vi.fn(async () => {
+      throw new ApiError('http', 'nope', 500)
+    })
+    const listHosts = vi.fn(async () => [])
+    const add = mountAddMachine(root, fakeApi({ requestPairingCode, listHosts }), { pollMs: 5 })
+    await add.start()
+    await flush()
+    expect(root.querySelector('.pair-error')?.textContent).toContain('Could not issue a code')
+    add.dispose()
+  })
+
+  it('renders the code via textContent only (no HTML injection)', async () => {
+    const requestPairingCode = vi.fn(async () => ({ code: '<img src=x>', expiresAt: futureIso() }))
+    const add = mountAddMachine(root, fakeApi({ requestPairingCode }), { pollMs: 100000 })
+    await add.start()
+    const cmd = root.querySelector('.pair-command') as HTMLElement
+    expect(cmd.querySelector('img')).toBeNull()
+    expect(cmd.textContent).toContain('<img src=x>')
+    add.dispose()
+  })
+})
+
+function futureIso(): string {
+  return new Date(Date.now() + 120_000).toISOString()
+}