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/default-terminal.test.ts

@@ -0,0 +1,72 @@
+import { describe, expect, it, vi } from 'vitest'
+import { deriveContentKey, encodeEnvelope, openReplayCiphertext, randomBytes, sealReplayFrame } from 'relay-e2e'
+
+// Mock the xterm modules so the DEFAULT (non-injected) terminal loaders run without a real canvas.
+const writes: string[] = []
+vi.mock('@xterm/xterm', () => ({
+  Terminal: class {
+    cols = 80
+    rows = 24
+    constructor(_opts?: unknown) {}
+    loadAddon(_a: unknown): void {}
+    open(_el: unknown): void {}
+    write(data: string): void {
+      writes.push(data)
+    }
+    onData(_cb: (d: string) => void): void {}
+    dispose(): void {}
+  },
+}))
+vi.mock('@xterm/addon-fit', () => ({
+  FitAddon: class {
+    fit(): void {}
+  },
+}))
+
+import { mountTerminalView } from '../src/terminal-view'
+import { mountPreviewClient, type ReplaySource } from '../src/preview-client'
+import type { TerminalTransport } from '../src/ws-transport'
+
+const tick = () => new Promise((r) => setTimeout(r, 0))
+
+describe('default (real-xterm) loaders behind the DI seam', () => {
+  it('mountTerminalView loads the default xterm + FitAddon and sends attach', async () => {
+    const root = document.createElement('div')
+    Object.defineProperty(root, 'clientWidth', { value: 100 })
+    Object.defineProperty(root, 'clientHeight', { value: 100 })
+    const sent: Uint8Array[] = []
+    const transport: TerminalTransport = {
+      open: async () => {},
+      send: (b) => sent.push(b),
+      onMessage: () => {},
+      onClose: () => {},
+      close: () => {},
+    }
+    const view = mountTerminalView(root, transport) // NO createTerminal → default loader path
+    await tick()
+    await tick()
+    const first = JSON.parse(new TextDecoder().decode(sent[0]!))
+    expect(first.type).toBe('attach')
+    view.dispose()
+  })
+
+  it('mountPreviewClient renders via the default read-only xterm loader', async () => {
+    const secret = randomBytes(32)
+    const k = deriveContentKey({ hostContentSecret: secret, sessionId: 's', alg: 'aes-256-gcm' })
+    const replay: ReplaySource = {
+      sessionId: 's',
+      alg: 'aes-256-gcm',
+      frames: [encodeEnvelope(sealReplayFrame(k, 0n, new TextEncoder().encode('DEFAULT-XTERM')))],
+    }
+    const card = document.createElement('div')
+    const client = mountPreviewClient(card, replay, secret, { cols: 80, rows: 24 }, {
+      deriveContentKey,
+      openReplayCiphertext,
+    })
+    await client.render()
+    await tick()
+    await tick()
+    expect(writes).toContain('DEFAULT-XTERM')
+    client.dispose()
+  })
+})