Use stable Windows process handles for job assignment

docs/roadmap/implementation.md

@@ -273,7 +273,7 @@ error presentation at the existing adapter-facing boundary.
 
 ## Stage 3 — Use The Stable Windows Process Handle
 
-**Status: Pending**
+**Status: Completed**
 
 ### Goal
 

internal/adapters/subprocess/process_tree_windows.go

@@ -39,19 +39,23 @@ func (tree *windowsProcessTree) Start(cmd *exec.Cmd) error {
 		return err
 	}
 
-	process, err := windows.OpenProcess(windows.PROCESS_SET_QUOTA|windows.PROCESS_TERMINATE, false, uint32(cmd.Process.Pid))
-	if err == nil {
-		err = windows.AssignProcessToJobObject(job, process)
-		_ = windows.CloseHandle(process)
+	var assignErr error
+	withHandleErr := cmd.Process.WithHandle(func(handle uintptr) {
+		assignErr = windows.AssignProcessToJobObject(job, windows.Handle(handle))
+	})
+	if withHandleErr == nil && assignErr == nil {
+		assignErr = resumeInitialThread(uint32(cmd.Process.Pid))
 	}
-	if err == nil {
-		err = resumeInitialThread(uint32(cmd.Process.Pid))
-	}
-	if err != nil {
+	if withHandleErr != nil || assignErr != nil {
 		killErr := cmd.Process.Kill()
 		waitErr := cmd.Wait()
 		_ = windows.CloseHandle(job)
-		return joinErrors(fmt.Errorf("assign process to job object: %w", err), killErr, waitErr)
+		return joinErrors(
+			fmt.Errorf("acquire process handle for job assignment: %w", withHandleErr),
+			fmt.Errorf("assign process to job object or resume initial thread: %w", assignErr),
+			killErr,
+			waitErr,
+		)
 	}
 
 	tree.job = job