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/preview-grid.test.ts

@@ -0,0 +1,112 @@
+import { describe, expect, it, vi } from 'vitest'
+import {
+  deriveContentKey,
+  encodeEnvelope,
+  openReplayCiphertext,
+  randomBytes,
+  sealReplayFrame,
+} from 'relay-e2e'
+import { mountPreviewGrid } from '../src/preview-grid'
+import type { PreviewDeps, ReplaySource } from '../src/preview-client'
+import type { ApiClient } from '../src/api-client'
+import type { HostRecord } from '../src/api-schemas'
+
+const ALG = 'aes-256-gcm' as const
+
+function host(sub: string): HostRecord {
+  return {
+    hostId: `id-${sub}`,
+    accountId: 'acc',
+    subdomain: sub,
+    agentPubkey: new Uint8Array([1]),
+    enrollFpr: `fpr-${sub}`,
+    status: 'online',
+    lastSeen: '2026-01-01T00:00:00Z',
+    createdAt: '2026-01-01T00:00:00Z',
+    revokedAt: null,
+  }
+}
+
+function sealed(sessionId: string, secret: Uint8Array, line: string): ReplaySource {
+  const k = deriveContentKey({ hostContentSecret: secret, sessionId, alg: ALG })
+  return { sessionId, alg: ALG, frames: [encodeEnvelope(sealReplayFrame(k, 0n, new TextEncoder().encode(line)))] }
+}
+
+function fakeApi(hosts: readonly HostRecord[]): ApiClient {
+  return {
+    listHosts: vi.fn(async () => hosts),
+    getHost: vi.fn(),
+    requestPairingCode: vi.fn(),
+    hostStatus: vi.fn(),
+    issueCapabilityToken: vi.fn(),
+  } as unknown as ApiClient
+}
+
+const realDeps: PreviewDeps = {
+  deriveContentKey,
+  openReplayCiphertext,
+  createTerminal: () => ({ open: () => {}, write: () => {}, dispose: () => {} }),
+}
+
+const flush = () => new Promise((r) => setTimeout(r, 0))
+
+describe('mountPreviewGrid (T9)', () => {
+  it('renders one preview card per authorized host', async () => {
+    const root = document.createElement('div')
+    const secret = randomBytes(32)
+    const loadReplay = vi.fn(async (hostId: string) => ({
+      replay: sealed(hostId, secret, 'screen'),
+      hostContentSecret: secret,
+    }))
+    const grid = mountPreviewGrid(root, fakeApi([host('a'), host('b')]), loadReplay, realDeps)
+    await flush()
+    await flush()
+    expect(root.querySelectorAll('.preview-card')).toHaveLength(2)
+    grid.dispose()
+  })
+
+  it('a host the account can\'t reach (loadReplay rejects) → "unavailable", never a foreign screen (INV1)', async () => {
+    const root = document.createElement('div')
+    const loadReplay = vi.fn(async () => {
+      throw new Error('forbidden')
+    })
+    const grid = mountPreviewGrid(root, fakeApi([host('a')]), loadReplay, realDeps)
+    await flush()
+    await flush()
+    expect(root.querySelector('.preview-unavailable')?.textContent).toBe('unavailable')
+    grid.dispose()
+  })
+
+  it('a listHosts failure renders a grid-level error, not a fabricated screen', async () => {
+    const root = document.createElement('div')
+    const api = {
+      listHosts: vi.fn(async () => {
+        throw new Error('unauth')
+      }),
+    } as unknown as ApiClient
+    const grid = mountPreviewGrid(root, api, vi.fn(), realDeps)
+    await flush()
+    expect(root.querySelector('.preview-grid-error')?.textContent).toBe('Could not load previews.')
+    grid.dispose()
+  })
+
+  it('dispose() tears down every preview client (no leaked xterms)', async () => {
+    const root = document.createElement('div')
+    const secret = randomBytes(32)
+    const disposed: string[] = []
+    const deps: PreviewDeps = {
+      deriveContentKey,
+      openReplayCiphertext,
+      createTerminal: () => ({ open: () => {}, write: () => {}, dispose: () => disposed.push('x') }),
+    }
+    const loadReplay = vi.fn(async (hostId: string) => ({
+      replay: sealed(hostId, secret, 'screen'),
+      hostContentSecret: secret,
+    }))
+    const grid = mountPreviewGrid(root, fakeApi([host('a')]), loadReplay, deps)
+    await flush()
+    await flush()
+    grid.dispose()
+    expect(disposed.length).toBeGreaterThan(0)
+  })
+})