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-e2e/test/errors.test.ts

@@ -0,0 +1,51 @@
+import { describe, expect, it } from 'vitest'
+import {
+  AeadOpenError,
+  CryptoUnavailableError,
+  E2EError,
+  EnvelopeFormatError,
+  FingerprintMismatchError,
+  HandshakeStateError,
+  ReplayError,
+} from '../src/errors.js'
+
+const SECRET_MARKER = 'SUPER_SECRET_KEY_BYTES_deadbeef'
+
+describe('T0 errors', () => {
+  const cases: Array<[E2EError, string]> = [
+    [new FingerprintMismatchError(), 'E2E_FINGERPRINT_MISMATCH'],
+    [new AeadOpenError(), 'E2E_AEAD_OPEN'],
+    [new ReplayError(), 'E2E_REPLAY'],
+    [new HandshakeStateError(), 'E2E_HANDSHAKE_STATE'],
+    [new EnvelopeFormatError(), 'E2E_ENVELOPE_FORMAT'],
+    [new CryptoUnavailableError(), 'E2E_CRYPTO_UNAVAILABLE'],
+  ]
+
+  it('every subclass extends E2EError and Error', () => {
+    for (const [err] of cases) {
+      expect(err).toBeInstanceOf(E2EError)
+      expect(err).toBeInstanceOf(Error)
+    }
+  })
+
+  it('each carries its stable code', () => {
+    for (const [err, code] of cases) {
+      expect(err.code).toBe(code)
+    }
+  })
+
+  it('name reflects the concrete subclass (stack legibility)', () => {
+    expect(new AeadOpenError().name).toBe('AeadOpenError')
+    expect(new ReplayError().name).toBe('ReplayError')
+  })
+
+  it('INV9: a caller-supplied message is never a secret sink — codes are fixed, not derived from key material', () => {
+    // The security property is that our OWN throw sites never interpolate secrets. Constructing an
+    // error with an accidental secret still must not change the stable code (callers surface code).
+    const e = new AeadOpenError(`open failed near ${SECRET_MARKER}`)
+    expect(e.code).toBe('E2E_AEAD_OPEN')
+    // Default-constructed errors (what our crypto paths throw) carry no secret.
+    expect(new AeadOpenError().message).not.toContain(SECRET_MARKER)
+    expect(new ReplayError().message).not.toContain('key')
+  })
+})