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.

term-relay/test/frame-codec.test.ts

@@ -0,0 +1,112 @@
+import { describe, test, expect } from 'vitest'
+import {
+  MUX_HEADER_BYTES,
+  encodeMuxFrame,
+  decodeHeader,
+  decodeMuxFrame,
+  encodeOpen,
+  decodeOpen,
+  encodeWindowUpdate,
+  decodeWindowUpdate,
+  encodeGoaway,
+  decodeGoaway,
+  TYPE_TO_BYTE,
+  BYTE_TO_TYPE,
+  type MuxFrameHeader,
+  type MuxFrameType,
+  type MuxOpen,
+} from '../mux/frame-codec.js'
+
+const ALL_TYPES: readonly MuxFrameType[] = [
+  'open',
+  'data',
+  'close',
+  'ping',
+  'pong',
+  'windowUpdate',
+  'goaway',
+]
+
+function header(over: Partial<MuxFrameHeader>): MuxFrameHeader {
+  return { version: 1, type: 'data', fin: false, rst: false, streamId: 7, payloadLen: 0, ...over }
+}
+
+describe('frame codec (T2, §4.1) — re-exported from the frozen relay-contracts codec', () => {
+  test('round-trips every frame type incl. fin/rst bit packing', () => {
+    for (const type of ALL_TYPES) {
+      const payload = new Uint8Array([1, 2, 3])
+      const h = header({ type, fin: true, rst: false, streamId: 42, payloadLen: payload.length })
+      const decoded = decodeMuxFrame(encodeMuxFrame(h, payload))
+      expect(decoded.header.type).toBe(type)
+      expect(decoded.header.fin).toBe(true)
+      expect(decoded.header.rst).toBe(false)
+      expect(decoded.header.streamId).toBe(42)
+      expect([...decoded.payload]).toEqual([1, 2, 3])
+    }
+  })
+
+  test('streamId=0 link-level frames decode with streamId===0', () => {
+    const h = header({ type: 'ping', streamId: 0, payloadLen: 0 })
+    expect(decodeHeader(encodeMuxFrame(h, new Uint8Array(0))).streamId).toBe(0)
+  })
+
+  test('rst bit round-trips independently of fin', () => {
+    const h = header({ type: 'close', fin: false, rst: true, payloadLen: 0 })
+    const d = decodeHeader(encodeMuxFrame(h, new Uint8Array(0)))
+    expect(d.rst).toBe(true)
+    expect(d.fin).toBe(false)
+  })
+
+  test('type ⇄ byte maps agree with §4.1 (0x01 OPEN … 0x07 GOAWAY)', () => {
+    expect(TYPE_TO_BYTE.open).toBe(0x01)
+    expect(TYPE_TO_BYTE.goaway).toBe(0x07)
+    expect(BYTE_TO_TYPE[0x02]).toBe('data')
+  })
+
+  test('negative: truncated buffer (< 15B) throws', () => {
+    expect(() => decodeHeader(new Uint8Array(MUX_HEADER_BYTES - 1))).toThrow()
+  })
+
+  test('negative: payloadLen larger than actual payload throws', () => {
+    const buf = encodeMuxFrame(header({ payloadLen: 2 }), new Uint8Array([9, 9]))
+    // Claim a longer payload than present.
+    buf[14] = 5
+    expect(() => decodeMuxFrame(buf)).toThrow()
+  })
+
+  test('negative: unknown type byte throws', () => {
+    const buf = encodeMuxFrame(header({ type: 'data', payloadLen: 0 }), new Uint8Array(0))
+    buf[1] = 0x08 // unknown type code
+    expect(() => decodeHeader(buf)).toThrow()
+    buf[1] = 0x00
+    expect(() => decodeHeader(buf)).toThrow()
+  })
+
+  test('negative: version ≠ 0x01 throws', () => {
+    const buf = encodeMuxFrame(header({ payloadLen: 0 }), new Uint8Array(0))
+    buf[0] = 0x02
+    expect(() => decodeHeader(buf)).toThrow()
+  })
+
+  test('OPEN payload round-trips via CBOR + Zod guard', () => {
+    const open: MuxOpen = {
+      streamId: 3,
+      subdomain: 'alice',
+      requestPath: '/term?join=x',
+      originHeader: 'https://alice.term.example.com',
+      remoteAddrHash: 'deadbeef',
+      capabilityTokenRef: 'jti-1',
+    }
+    expect(decodeOpen(encodeOpen(open))).toEqual(open)
+  })
+
+  test('decodeOpen rejects a malformed/partial CBOR payload (never returns partial)', () => {
+    expect(() => decodeOpen(new Uint8Array([0x00, 0x01, 0x02]))).toThrow()
+  })
+
+  test('WINDOW_UPDATE + GOAWAY int codecs round-trip', () => {
+    expect(decodeWindowUpdate(encodeWindowUpdate(65_536))).toBe(65_536)
+    const g = decodeGoaway(encodeGoaway(9, 'revoked'))
+    expect(g).toEqual({ lastStreamId: 9, reason: 'revoked' })
+  })
+})