fix: bind Cua pixel actions to current screenshot geometry

Correct native scroll scaling, reject stale or out-of-bounds pixel targets, and scope DPI awareness to geometry reads. Package adapter 0.36.0+artemis.3 and document the high-effort cross-device verification.

Validation: Go tests and vet, packaged MCP schema and handshake, Python checks, and user-run high-effort task completed with a passed verdict and explicit coverage limits.

plugins/cua-driver/windows.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"os/exec"
+	"runtime"
 	"syscall"
 	"unsafe"
 )
@@ -12,7 +13,6 @@ var kernel32 = syscall.NewLazyDLL("kernel32.dll")
 
 func configureProcess(c *exec.Cmd) {
 	c.SysProcAttr = &syscall.SysProcAttr{HideWindow: true}
-	user32.NewProc("SetThreadDpiAwarenessContext").Call(^uintptr(3))
 }
 func windowOwned(pid, hwnd int64) bool {
 	var actual uint32
@@ -24,6 +24,17 @@ func windowOwned(pid, hwnd int64) bool {
 	return int64(actual) == pid
 }
 func verifyWindow(pid, hwnd int64, b obj) (obj, bool) {
+	// DPI context belongs to an OS thread, not a Go goroutine. Apply it around
+	// the actual geometry reads; setting it once while starting a child leaks
+	// context and later GetSystemMetrics can return virtualized dimensions.
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+	setDPI := user32.NewProc("SetThreadDpiAwarenessContext")
+	previous, _, _ := setDPI.Call(^uintptr(3))
+	if previous == 0 {
+		return nil, false
+	}
+	defer setDPI.Call(previous)
 	if !windowOwned(pid, hwnd) {
 		return nil, false
 	}