fix(desktop): report real hostname/platform/arch in heartbeat

Renderer was registering clients with navigator.platform ("MacIntel") and
a hardcoded "renderer-preview" cpu_arch. Source device info from the main
process (os.hostname + process.platform/arch) via a new device-info IPC,
and let heartbeats always send the authoritative runtime values so stale
registrations self-heal.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/desktop-client/src/main/runtime-controller.ts

@@ -1,3 +1,5 @@
+import { hostname } from "node:os";
+
 import { ApiClientError } from "@geo/http-client";
 import type {
   DesktopArticleContent,
@@ -489,9 +491,9 @@ async function sendHeartbeat(source: "startup" | "timer"): Promise<void> {
 
   try {
     const response = await heartbeatDesktopClient({
-      device_name: state.client?.device_name ?? `Desktop ${process.platform}`,
-      os: state.client?.os ?? process.platform,
-      cpu_arch: state.client?.cpu_arch ?? process.arch,
+      device_name: hostname() || state.client?.device_name || `Desktop ${process.platform}`,
+      os: process.platform,
+      cpu_arch: process.arch,
       client_version: state.client?.client_version ?? "0.1.0-dev",
       channel: state.client?.channel ?? "dev",
       account_ids: state.accounts.filter((account) => account.health === "live").map((account) => account.id),