Restructure solution layout by module

src/Scanner/StellaOps.Scanner.Sbomer.BuildXPlugin/BuildxPluginException.cs

@@ -0,0 +1,19 @@
+using System;
+
+namespace StellaOps.Scanner.Sbomer.BuildXPlugin;
+
+/// <summary>
+/// Represents user-facing errors raised by the BuildX plug-in.
+/// </summary>
+public sealed class BuildxPluginException : Exception
+{
+    public BuildxPluginException(string message)
+        : base(message)
+    {
+    }
+
+    public BuildxPluginException(string message, Exception innerException)
+        : base(message, innerException)
+    {
+    }
+}