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.

agent/test/csr.test.ts

@@ -0,0 +1,32 @@
+import { describe, expect, it } from 'vitest'
+import { X509Certificate } from 'node:crypto'
+import { generateIdentity } from '../src/keys/identity.js'
+import { buildCsr } from '../src/enroll/csr.js'
+
+describe('PKCS#10 CSR (T4)', () => {
+  it('emits a PEM CERTIFICATE REQUEST', () => {
+    const csr = buildCsr(generateIdentity(), 'host-42.term.example.com')
+    expect(csr).toContain('-----BEGIN CERTIFICATE REQUEST-----')
+    expect(csr).toContain('-----END CERTIFICATE REQUEST-----')
+  })
+
+  it('does not contain private-key material (INV4)', () => {
+    const id = generateIdentity()
+    const csr = buildCsr(id, 'host-42')
+    expect(csr).not.toContain('PRIVATE KEY')
+    expect(csr).not.toContain(id.exportPrivatePkcs8Pem().split('\n')[1]!)
+  })
+
+  it('produces a syntactically decodable DER structure', () => {
+    // Node can't parse a CSR directly, but the base64 body must be valid DER (a SEQUENCE).
+    const csr = buildCsr(generateIdentity(), 'host-42')
+    const b64 = csr
+      .replace(/-----[A-Z ]+-----/g, '')
+      .replace(/\s+/g, '')
+    const der = Buffer.from(b64, 'base64')
+    expect(der[0]).toBe(0x30) // outer SEQUENCE tag
+    expect(der.length).toBeGreaterThan(64)
+    // sanity: X509Certificate exists (crypto available) — unrelated smoke to keep import used
+    expect(typeof X509Certificate).toBe('function')
+  })
+})