bug: Issues with subprocess management in Windows

[gau-nernst]

Cortex version

dev

Describe the issue and expected behaviour

2 main issues

1. pid_t on windows is DWORD (unsigned long), but we return -1 to signal failure

cortex.cpp/engine/utils/process/utils.h

Lines 3 to 6 in ca2327a

	#if defined(_WIN32)
	#include <process.h>
	#include <windows.h>
	using pid_t = DWORD;

cortex.cpp/engine/utils/process/utils.cc

Lines 102 to 104 in ca2327a

	} catch (const std::exception& e) {
	LOG_ERROR << "Process spawning error: " << e.what();
	return -1;

Perhaps we can use another value for failure e.g. 0, or use cpp::result like many other parts of the codebase.

2. TerminateProcess() does not kill children processes

cortex.cpp/engine/utils/process/utils.cc

Line 159 in ca2327a

bool is_success = TerminateProcess(hProcess, 0) == TRUE;

The solution is to use Job object https://devblogs.microsoft.com/oldnewthing/20131209-00/?p=2433

Edit: Issue 2 is more complex than I previously thought. Initially I thought Mac and Linux kill children process, but turns out it was because I was testing with uv, and we kill uv process by sending SIGTERM, which uv will propagate the signal to the children processes. If we kill uv process with SIGKILL, actually the children process will also be left hanging. Need to think of a better way for this...

Assigning this to me since this is required for my Python engine PR.

Steps to Reproduce

No response

Screenshots / Logs

No response

What is your OS?

• Windows
• Mac Silicon
• Mac Intel
• Linux / Ubuntu

What engine are you running?

• cortex.llamacpp (default)
• cortex.tensorrt-llm (Nvidia GPUs)
• cortex.onnx (NPUs, DirectML)

Hardware Specs eg OS version, GPU

No response