Function resume_main_thread 

pub(crate) fn resume_main_thread(pid: u32) -> Result<(), String>

Resume the (single) main thread of a CREATE_SUSPENDED process.

Walks a Toolhelp32 thread snapshot to find the one thread belonging to pid (a freshly-spawned suspended process has only its main thread), opens it with THREAD_SUSPEND_RESUME, and ResumeThread’s it.

Errors come from snapshot creation, OpenThread, or ResumeThread returning (DWORD)-1. A ResumeThread return of 0 means the thread was already running (impossible if the process was just created suspended) — treated as success.