fix(desktop): bundle arm64 binaries for windows arm

[mweinbach]

Issue for this PR

Closes #45875

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Fixes two places where the Windows ARM64 desktop build bundled x64 native binaries:

1. In CI, the aarch64-pc-windows-msvc Electron job runs on an x64 windows-2025 host without bun_install_flags: --cpu=*, and electron.vite.config.ts resolved @lydell/node-pty using process.platform/process.arch instead of OPENCODE_CLI_TARGET. As a result, opencode-desktop-win-arm64.exe packaged @lydell/node-pty-win32-x64. This resolves the node-pty package from OPENCODE_CLI_TARGET, installs --cpu=* for the Windows ARM64 CI build, excludes non-target @lydell/node-pty-* packages from electron-builder, and verifies the target conpty.node prebuild in afterPack.
2. packages/core pinned bun-pty to 0.4.9, which only shipped an x64 rust_pty.dll and embedded it into cli-windows-arm64/bin/opencode.exe (failing dlopen with Windows error 193 on ARM64). Bumping bun-pty to 0.4.11 embeds rust_pty_arm64.dll when compiling for win32-arm64.
3. Evaluates the electron-vite and electron-builder configs directly in their unit tests instead of spawning esbuild via loadConfigFromFile on every call, cutting those two test files from ~7.6s to ~1.7s.

How did you verify your code works?

• Ran bun test ./electron.vite.config.test.ts ./electron-builder.config.test.ts in packages/desktop (verifying cross-architecture OPENCODE_CLI_TARGET resolution and FileMatcher filtering across all targets).
• Ran bun typecheck in packages/core and bun run lint:changed.
• Verified rust_pty_arm64.dll in bun-pty@0.4.11 has PE machine type 0xaa64 (ARM64).

Screenshots / recordings

N/A (build and packaging fix)

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

---

Added by the opencode bot (AI-generated).

Related: #44664

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍

[opencode-agent]

The change looks correct. I couldn't verify it end to end, because that needs a Windows ARM64 CI build and machine.

On Linux I loaded both configs through the loaders the build tools actually use: electron-vite's loadConfigFromFile, and jiti for electron-builder.

• With OPENCODE_CLI_TARGET=aarch64-pc-windows-msvc, the main build externalizes @lydell/node-pty-win32-arm64, and electron-builder excludes the other five node-pty packages. Without a target, both still fall back to the host.
• The afterPack path matches the published @lydell/node-pty-win32-arm64@1.2.0-beta.12 layout (prebuilds/win32-arm64/conpty.node).
• bun-pty 0.4.11 ships rust_pty_arm64.dll and selects it on win32/arm64.
• The desktop config tests pass (9/9), and tsgo -b is clean.

Public API: unchanged. OPENCODE_CLI_TARGET was already read by the desktop scripts; it now also drives the vite and electron-builder configs, with the same host fallback, and is set in the publish workflow's packaging steps.

No blocking concerns.

Related: #44664