fix: 高亮框初始隐藏，仅有效矩形时显示

resources/desktop-picker.ps1

@@ -79,6 +79,10 @@ $hl.Show()
 $stage = "hover"
 $chain = New-Object System.Collections.ArrayList
 $selIdx = -1
+$script:lastX = -1
+$script:lastY = -1
+$script:lastMove = Get-Date
+$script:pending = $false
 $prevSpace = $false
 $prevPgUp = $false
 $prevPgDn = $false
@@ -94,6 +98,13 @@ while ($true) {
   if ($stage -eq "hover") {
     $ptX = [System.Windows.Forms.Cursor]::Position.X
     $ptY = [System.Windows.Forms.Cursor]::Position.Y
+    if ($ptX -ne $script:lastX -or $ptY -ne $script:lastY) {
+      $script:lastX = $ptX; $script:lastY = $ptY
+      $script:lastMove = Get-Date
+      $script:pending = $true
+    }
+    $idle = ((Get-Date) - $script:lastMove).TotalMilliseconds -ge 250
+    if (-not $idle) { Start-Sleep -Milliseconds 60; return }
     $el = Get-DeepestAtPoint $ptX $ptY
     if ($el) {
       $c = $el.Current