add Store listing images: 9:16 poster and 300x300 logo

Partner Center's screenshots and logos steps needed sizes the MSIX package
doesn't produce, so they are drawn separately with the same mark.

Packaging/New-Poster.ps1

@@ -0,0 +1,84 @@
+<#
+.SYNOPSIS
+    Draws the Store 9:16 poster (720x1080), matching the mark drawn by
+    Packaging\New-Assets.ps1 (a dark plate with a white "Aя").
+
+.DESCRIPTION
+    One-off script, not part of the packaging pipeline: this poster is a Store
+    listing image, uploaded by hand in Partner Center rather than shipped
+    inside the MSIX, so it does not belong next to the logos that build feeds
+    into the package.
+#>
+[CmdletBinding()]
+param(
+    [string] $OutPath = (Join-Path $PSScriptRoot 'Poster720x1080.png')
+)
+
+Set-StrictMode -Version Latest
+$ErrorActionPreference = 'Stop'
+
+Add-Type -AssemblyName System.Drawing
+
+$Width = 720
+$Height = 1080
+$Background = [System.Drawing.Color]::FromArgb(255, 0x20, 0x20, 0x20)
+$Foreground = [System.Drawing.Color]::FromArgb(255, 0xFF, 0xFF, 0xFF)
+$Glyph = 'Aя'
+
+$bitmap = New-Object System.Drawing.Bitmap($Width, $Height, [System.Drawing.Imaging.PixelFormat]::Format32bppArgb)
+$graphics = [System.Drawing.Graphics]::FromImage($bitmap)
+
+try {
+    $graphics.SmoothingMode = [System.Drawing.Drawing2D.SmoothingMode]::AntiAlias
+    $graphics.TextRenderingHint = [System.Drawing.Text.TextRenderingHint]::AntiAliasGridFit
+
+    # Full bleed: Partner Center masks/rounds the poster itself, so the plate
+    # here just fills the whole canvas rather than drawing its own corners
+    $graphics.Clear($Background)
+
+    # The glyph is sized off the width, the narrower of the two dimensions,
+    # the same way New-Assets.ps1 sizes it off the shorter side of a square
+    [System.Drawing.StringFormat] $format = [System.Drawing.StringFormat]::GenericTypographic.Clone()
+
+    try {
+        $target = $Width * 0.62
+        $ceiling = $Height * 0.30
+        $fontSize = $Width * 0.9
+        $font = $null
+        $measured = $null
+
+        for ($attempt = 0; $attempt -lt 20; $attempt++) {
+            if ($font) { $font.Dispose() }
+            $font = New-Object System.Drawing.Font('Segoe UI', $fontSize, [System.Drawing.FontStyle]::Bold, [System.Drawing.GraphicsUnit]::Pixel)
+            $measured = $graphics.MeasureString($Glyph, $font, ([System.Drawing.PointF]::new(0, 0)), $format)
+
+            if ($measured.Width -le $target -and $measured.Height -le $ceiling) { break }
+
+            $scale = [Math]::Min($target / $measured.Width, $ceiling / $measured.Height)
+            $fontSize = $fontSize * $scale * 0.98
+        }
+
+        try {
+            $x = [Math]::Round(($Width - $measured.Width) / 2.0)
+            $y = [Math]::Round(($Height - $measured.Height) / 2.0)
+
+            $brush = New-Object System.Drawing.SolidBrush($Foreground)
+            $origin = New-Object System.Drawing.PointF($x, $y)
+
+            try { $graphics.DrawString($Glyph, $font, $brush, $origin, $format) }
+            finally { $brush.Dispose() }
+        }
+        finally {
+            $font.Dispose()
+        }
+    }
+    finally {
+        $format.Dispose()
+    }
+}
+finally {
+    $graphics.Dispose()
+}
+
+try { $bitmap.Save($OutPath, [System.Drawing.Imaging.ImageFormat]::Png) } finally { $bitmap.Dispose() }
+Write-Host "Saved $OutPath"