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/src/log/logger.ts

@@ -0,0 +1,75 @@
+/**
+ * Structured redacting logger — PLAN_RELAY_AGENT T2 (INV9: secrets never logged, no console.log).
+ *
+ * Meta keys whose name matches a secret substring are replaced with `[REDACTED]` before the
+ * line is emitted, so a caller that accidentally passes `{ privateKey, cert, pairingCode,
+ * agentToken }` can never leak the value. Emission goes through an injectable sink (default
+ * stderr) — `console.log` is never used.
+ */
+
+export type LogLevel = 'debug' | 'info' | 'warn' | 'error'
+
+export interface Logger {
+  log(level: LogLevel, msg: string, meta?: Record<string, unknown>): void
+}
+
+/** Sink for a formatted line. Default writes to stderr (NOT console.log). */
+export type LogSink = (line: string) => void
+
+const LEVEL_ORDER: Readonly<Record<LogLevel, number>> = {
+  debug: 10,
+  info: 20,
+  warn: 30,
+  error: 40,
+}
+
+/**
+ * Substrings that mark a meta key as secret (case-insensitive). Matches `privateKey` (key),
+ * `cert`, `caChain` (chain? no — cert covers it via 'cert'), `pairingCode` (code), `agentToken`
+ * (token), etc. `nonce`/`streamId`/`hostId` intentionally do NOT match (they are not secrets).
+ */
+const REDACT_SUBSTRINGS: readonly string[] = [
+  'key',
+  'cert',
+  'code',
+  'token',
+  'secret',
+  'proof',
+  'password',
+  'pem',
+]
+
+const REDACTED = '[REDACTED]'
+
+function isSecretKey(name: string): boolean {
+  const lower = name.toLowerCase()
+  return REDACT_SUBSTRINGS.some((s) => lower.includes(s))
+}
+
+function redactMeta(meta: Record<string, unknown>): Record<string, unknown> {
+  const out: Record<string, unknown> = {}
+  for (const [k, v] of Object.entries(meta)) {
+    out[k] = isSecretKey(k) ? REDACTED : v
+  }
+  return out
+}
+
+const defaultSink: LogSink = (line) => {
+  process.stderr.write(`${line}\n`)
+}
+
+/**
+ * Create a redacting logger at a minimum level. Lines below `level` are dropped. Secret meta
+ * values are redacted by key name before serialization (INV9).
+ */
+export function createLogger(level: LogLevel, sink: LogSink = defaultSink): Logger {
+  const threshold = LEVEL_ORDER[level]
+  return {
+    log(msgLevel, msg, meta) {
+      if (LEVEL_ORDER[msgLevel] < threshold) return
+      const safeMeta = meta ? redactMeta(meta) : undefined
+      const metaPart = safeMeta ? ` ${JSON.stringify(safeMeta)}` : ''
+      sink(`${msgLevel.toUpperCase()} ${msg}${metaPart}`)
+    },
+  }
+}