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/src/preview-grid.ts

@@ -0,0 +1,87 @@
+/**
+ * T9 (v0.10) — grid of `preview-client` cards (the manage-page moved CLIENT-SIDE under E2E).
+ *
+ * Renders one read-only, locally-decrypted preview per authorized host. A host the account can't
+ * reach → `loadReplay` rejects → the card shows "unavailable", never another tenant's screen
+ * (INV1). Disposes all preview clients on unmount so no xterms/sockets leak (EXPLORE §6 preview-cost
+ * discipline); `hostContentSecret` is never written to `localStorage`/`console`.
+ */
+import type { ApiClient } from './api-client'
+import type { HostRecord } from './api-schemas'
+import {
+  mountPreviewClient,
+  type PreviewClient,
+  type PreviewDeps,
+  type ReplaySource,
+} from './preview-client'
+
+const DEFAULT_DIMS = { cols: 80, rows: 24 } as const
+
+export interface PreviewGridOpts {
+  readonly dims?: { cols: number; rows: number }
+}
+
+export function mountPreviewGrid(
+  root: HTMLElement,
+  api: ApiClient,
+  loadReplay: (
+    hostId: string,
+  ) => Promise<{ replay: ReplaySource; hostContentSecret: Uint8Array }>,
+  deps: PreviewDeps,
+  opts: PreviewGridOpts = {},
+): { dispose(): void } {
+  const dims = opts.dims ?? DEFAULT_DIMS
+  const clients: PreviewClient[] = []
+  let disposed = false
+
+  function unavailableCard(host: HostRecord): HTMLElement {
+    const card = document.createElement('div')
+    card.className = 'preview-card'
+    card.dataset['hostId'] = host.hostId
+    const msg = document.createElement('p')
+    msg.className = 'preview-unavailable'
+    msg.textContent = 'unavailable'
+    card.append(msg)
+    return card
+  }
+
+  async function build(): Promise<void> {
+    let hosts: readonly HostRecord[]
+    try {
+      hosts = await api.listHosts()
+    } catch {
+      const err = document.createElement('p')
+      err.className = 'preview-grid-error'
+      err.textContent = 'Could not load previews.'
+      root.append(err)
+      return
+    }
+    if (disposed) return
+
+    for (const host of hosts) {
+      const card = document.createElement('div')
+      card.className = 'preview-card'
+      card.dataset['hostId'] = host.hostId
+      root.append(card)
+      try {
+        const { replay, hostContentSecret } = await loadReplay(host.hostId)
+        if (disposed) return
+        const client = mountPreviewClient(card, replay, hostContentSecret, dims, deps)
+        clients.push(client)
+        await client.render()
+      } catch {
+        // A host the account can't reach (403) or a decrypt failure → "unavailable" (INV1).
+        card.replaceWith(unavailableCard(host))
+      }
+    }
+  }
+
+  void build()
+
+  return {
+    dispose(): void {
+      disposed = true
+      for (const c of clients) c.dispose() // no leaked xterms/sockets
+    },
+  }
+}