fix: pipe binding test output on Windows

[mikemikimike]

Fixes #638

On Windows, fork() with all stdio streams ignored can exit before the binding test child sends its ready message. This makes the Vulkan prebuilt binding appear unavailable and can trigger an unnecessary source build.

This change defaults the binding test's child output streams to pipes on Windows, and makes the public getLlamaForOptions path use the same platform-specific default. Explicit pipeOutputOnNode and pipeBinaryTestErrorLogs values still take precedence.

Added a mocked IPC regression test covering the Windows default and the explicit override.

Validation:

• npm run test:typescript
• npm exec -- vitest run test/standalone/bindings/testBindingBinary.test.ts --reporter=verbose --pool=forks --maxWorkers=1
• npm run lint:eslint
• npm run format
• npm run build
• git diff --check

The full standalone suite was attempted, but its local llama.cpp CMake/MSBuild build did not complete in this Windows environment; no external API or GPU service was used by the regression test.