feat: add Windows ARM64 support with x64-baseline CLI workaround (#2537)

* feat: add Windows ARM64 support with x64-baseline CLI workaround

Windows ARM64 native opencode.exe fails with a Bun FFI/TinyCC dlopen
error (anomalyco/opencode#19130). As a temporary workaround:

- Bundle x64-baseline OpenCode CLI on ARM64 instead of native ARM64
  (prepare-opencode-cli.mjs, env-runtime.js)
- Disable OpenCode self-upgrade on ARM64 in server, VS Code, and UI
  (upgrade-capability.js, opencode-upgrade-runtime.ts, useUIStore.ts,
  OpenCodeCliSettings.tsx, search.ts, SettingsView.tsx, platform.ts)
- Add ARM64 Windows cross-compile builds to release and smoke workflows
  (release.yml, release-desktop-smoke.yml)
- Refactor Windows latest.yml to use combine-electron-manifests pattern
  matching macOS, since two arches now produce per-arch manifests

The CI ARM64 build itself is permanent; only the x64-baseline CLI
bundling and upgrade disablement are temporary and should be reverted
when the upstream issue is resolved.

* fix(desktop): select Windows updater by architecture

---------

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/vscode/src/opencode-upgrade-runtime.ts

@@ -1,7 +1,7 @@
 type UpgradeCapability = {
   supported: boolean;
-  manager: 'opencode' | 'external' | null;
-  reason: 'external' | 'unavailable' | null;
+  manager: 'opencode' | 'external' | 'openchamber' | null;
+  reason: 'external' | 'unavailable' | 'windows-arm64-workaround' | null;
 };
 
 export type OpenCodeUpgradeManager = {
@@ -15,6 +15,12 @@ type UpgradeResult = { status: number; body: Record<string, unknown> };
 
 let openCodeUpgradePromise: Promise<UpgradeResult> | null = null;
 
+// TEMPORARY WORKAROUND — Windows ARM64: native opencode.exe fails with a Bun
+// FFI/TinyCC dlopen error (https://github.com/anomalyco/opencode/issues/19130).
+// Disable OpenCode self-upgrade on ARM64 so it can't overwrite the working x64
+// binary with the broken ARM64 build. Remove when the upstream issue is resolved.
+const isWindowsArm64 = (): boolean => process.platform === 'win32' && process.arch === 'arm64';
+
 const parseVersion = (value: unknown): { parts: number[]; prerelease: boolean } => {
   const normalized = String(value || '').replace(/^v/, '').split('+')[0];
   const prereleaseIndex = normalized.indexOf('-');
@@ -39,6 +45,7 @@ const compareVersions = (left: unknown, right: unknown): number => {
 };
 
 const getCapability = (manager?: OpenCodeUpgradeManager): UpgradeCapability => {
+  if (isWindowsArm64()) return { supported: false, manager: 'openchamber', reason: 'windows-arm64-workaround' };
   if (!manager) return { supported: false, manager: null, reason: 'unavailable' };
   if (manager.getDebugInfo().mode !== 'managed') return { supported: false, manager: 'external', reason: 'external' };
   if (!manager.getApiUrl()) return { supported: false, manager: null, reason: 'unavailable' };