Initial commit: Theriapolis baseline at port/godot branch point

Captures the pre-Godot-port state of the codebase. This is the rollback
anchor for the Godot port (M0 of theriapolis-rpg-implementation-plan-godot-port.md).
All Phase 0 through Phase 6.5 work is included; Phase 7 is in flight.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Theriapolis.Game/Platform/Clipboard.cs

@@ -0,0 +1,20 @@
+using System.Runtime.InteropServices;
+
+namespace Theriapolis.Game.Platform;
+
+/// <summary>
+/// Cross-platform clipboard writer via SDL2, which MonoGame.Framework.DesktopGL
+/// already loads. Silently no-ops if the native call fails so debug-only callers
+/// never crash the game.
+/// </summary>
+public static class Clipboard
+{
+    [DllImport("SDL2", EntryPoint = "SDL_SetClipboardText", CallingConvention = CallingConvention.Cdecl)]
+    private static extern int SDL_SetClipboardText([MarshalAs(UnmanagedType.LPUTF8Str)] string text);
+
+    public static bool TrySetText(string text)
+    {
+        try { return SDL_SetClipboardText(text) == 0; }
+        catch { return false; }
+    }
+}