feat: add Windows computer-use plugin adapter and validation tools

plugins/open-computer-use/window-capture.ps1

@@ -0,0 +1,59 @@
+# ARTEMIS adapter for open-computer-use@1.1.0 (MIT).
+# Never fall back to CopyFromScreen: an overlapping window is not test evidence.
+function Capture-WindowPngBase64($bounds, [IntPtr]$hwnd) {
+    if ($hwnd -eq [IntPtr]::Zero) { return $null }
+    if (-not (Test-CapturableFrame $bounds)) {
+        return $null
+    }
+    $bitmap = $null
+    $graphics = $null
+    $stream = $null
+    $hdc = [IntPtr]::Zero
+    try {
+        $frame = Get-CapturableWindowFrame $hwnd
+        if ($null -eq $frame -or $frame.x -ne $bounds.x -or $frame.y -ne $bounds.y -or
+            $frame.width -ne $bounds.width -or $frame.height -ne $bounds.height) {
+            return $null
+        }
+        $bitmap = New-Object System.Drawing.Bitmap ([int][math]::Round($bounds.width)), ([int][math]::Round($bounds.height))
+        $graphics = [System.Drawing.Graphics]::FromImage($bitmap)
+        $graphics.Clear([System.Drawing.Color]::Black)
+        $hdc = $graphics.GetHdc()
+        # PW_RENDERFULLCONTENT also asks modern applications to render their surface.
+        # The upstream 30-second subprocess budget bounds an unresponsive WM_PRINT.
+        $captured = [OCUWin32]::PrintWindow($hwnd, $hdc, 2)
+        $graphics.ReleaseHdc($hdc)
+        $hdc = [IntPtr]::Zero
+        if (-not $captured) { return $null }
+        $after = Get-CapturableWindowFrame $hwnd
+        if ($null -eq $after -or $after.x -ne $frame.x -or $after.y -ne $frame.y -or
+            $after.width -ne $frame.width -or $after.height -ne $frame.height) {
+            return $null
+        }
+        # Some applications return success without rendering. Reject uniform frames;
+        # a usable UI tree remains available even when a window cannot be captured.
+        $first = $bitmap.GetPixel(0, 0).ToArgb()
+        $hasContent = $false
+        for ($row = 0; $row -lt 17 -and -not $hasContent; $row++) {
+            for ($column = 0; $column -lt 17; $column++) {
+                $x = [int][math]::Floor(($bitmap.Width - 1) * $column / 16)
+                $y = [int][math]::Floor(($bitmap.Height - 1) * $row / 16)
+                if ($bitmap.GetPixel($x, $y).ToArgb() -ne $first) {
+                    $hasContent = $true
+                    break
+                }
+            }
+        }
+        if (-not $hasContent) { return $null }
+        $stream = New-Object System.IO.MemoryStream
+        $bitmap.Save($stream, [System.Drawing.Imaging.ImageFormat]::Png)
+        return [Convert]::ToBase64String($stream.ToArray())
+    } catch {
+        return $null
+    } finally {
+        if ($hdc -ne [IntPtr]::Zero -and $null -ne $graphics) { $graphics.ReleaseHdc($hdc) }
+        if ($null -ne $graphics) { $graphics.Dispose() }
+        if ($null -ne $bitmap) { $bitmap.Dispose() }
+        if ($null -ne $stream) { $stream.Dispose() }
+    }
+}