fix: Windows screenshot only captured top-left on HiDPI displays

PowerShell.exe / pwsh.exe run as DPI-unaware by default, so Windows
virtualizes coordinates for any WinForms call: on a 4K display at
200% scaling, PrimaryScreen.Bounds reported 1920x1080 and
CopyFromScreen dutifully grabbed only the top-left quarter of the
real framebuffer. Result: the screenshot 'could not fit full
screen' even though nothing was technically wrong with the capture
call.

Declare per-monitor DPI awareness before touching any Screen API.
Use SetProcessDpiAwarenessContext(PER_MONITOR_V2) on Windows 10+,
fall back to SetProcessDPIAware on older Windows. After this,
PrimaryScreen.Bounds returns real physical pixels and the capture
covers the whole primary display.

Also add a -VirtualDesktop switch so future multi-monitor callers
can request the full joined virtual screen. Default stays on
PrimaryScreen to keep the existing 'main_display' semantics.

Author: ouyyyyang

scripts/windows/capture-screen.ps1

@@ -1,19 +1,81 @@
 param(
     [Parameter(Mandatory = $true)]
-    [string]$OutputPath
+    [string]$OutputPath,
+    [switch]$VirtualDesktop
 )
 
 $ErrorActionPreference = "Stop"
 
 Add-Type -AssemblyName System.Windows.Forms
 Add-Type -AssemblyName System.Drawing
 
+# Declare per-monitor DPI awareness BEFORE touching any WinForms Screen
+# API. PowerShell.exe / pwsh.exe are DPI-unaware by default, so without
+# this call Windows virtualizes coordinates: on a 4K display at 200%
+# scaling, PrimaryScreen.Bounds would report 1920x1080 and CopyFromScreen
+# would grab only the top-left quarter of the real framebuffer. The
+# symptom looks like "the screenshot does not fit full screen".
+#
+# We try the Windows 10 per-monitor API first and fall back to the
+# older process-wide API that ships in every Windows version since 7.
+$dpiTypes = @"
+using System;
+using System.Runtime.InteropServices;
+
+public static class ScreenPilotDpi
+{
+    [DllImport("user32.dll")]
+    private static extern bool SetProcessDpiAwarenessContext(IntPtr dpiContext);
+
+    [DllImport("user32.dll")]
+    private static extern bool SetProcessDPIAware();
+
+    // DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2 = -4
+    private static readonly IntPtr PerMonitorV2 = new IntPtr(-4);
+
+    public static void Apply()
+    {
+        try
+        {
+            if (SetProcessDpiAwarenessContext(PerMonitorV2))
+            {
+                return;
+            }
+        }
+        catch
+        {
+        }
+
+        try
+        {
+            SetProcessDPIAware();
+        }
+        catch
+        {
+        }
+    }
+}
+"@
+
+if (-not ("ScreenPilotDpi" -as [type])) {
+    Add-Type -TypeDefinition $dpiTypes -Language CSharp
+}
+[ScreenPilotDpi]::Apply()
+
 $outputDirectory = Split-Path -Parent $OutputPath
 if ($outputDirectory -and -not (Test-Path -LiteralPath $outputDirectory)) {
     New-Item -ItemType Directory -Path $outputDirectory -Force | Out-Null
 }
 
-$bounds = [System.Windows.Forms.Screen]::PrimaryScreen.Bounds
+# Default to the primary display, which matches the "main_display"
+# capture target semantics used by the agent. Pass -VirtualDesktop to
+# capture every monitor joined into one image.
+if ($VirtualDesktop) {
+    $bounds = [System.Windows.Forms.SystemInformation]::VirtualScreen
+} else {
+    $bounds = [System.Windows.Forms.Screen]::PrimaryScreen.Bounds
+}
+
 $bitmap = New-Object System.Drawing.Bitmap $bounds.Width, $bounds.Height
 $graphics = [System.Drawing.Graphics]::FromImage($bitmap)