feat(release): add cross-platform packaging

Add target-aware engine provisioning, platform package configs, and CI/release verification for macOS arm64, Windows x64, and Linux AppImage.

src/utils/platform.ts

@@ -0,0 +1,45 @@
+import { useEffect, useState } from 'react';
+import type { PlatformInfo } from '../bindings/PlatformInfo';
+import { invokeCommand as invoke } from '../ipc';
+
+const fallback: PlatformInfo = {
+  os: 'unknown',
+  arch: 'unknown',
+  targetTriple: 'unknown'
+};
+
+let cached: PlatformInfo | null = null;
+let pending: Promise<PlatformInfo> | null = null;
+
+export const getPlatformInfo = (): Promise<PlatformInfo> => {
+  if (cached) return Promise.resolve(cached);
+  if (!pending) {
+    pending = invoke('get_platform_info')
+      .then(info => {
+        cached = info;
+        return info;
+      })
+      .finally(() => {
+        pending = null;
+      });
+  }
+  return pending;
+};
+
+export const usePlatformInfo = () => {
+  const [platform, setPlatform] = useState<PlatformInfo>(cached ?? fallback);
+
+  useEffect(() => {
+    let active = true;
+    void getPlatformInfo()
+      .then(info => {
+        if (active) setPlatform(info);
+      })
+      .catch(() => undefined);
+    return () => {
+      active = false;
+    };
+  }, []);
+
+  return platform;
+};