phase(N.5) Task 1: ArbBindlessTexture wrapper + capability detection

Adds Silk.NET.OpenGL.Extensions.ARB 2.23.0 package and a thin
BindlessSupport wrapper exposing GetResidentHandle / MakeNonResident /
HasShaderDrawParameters. TryCreate returns false if the bindless
extension isn't present, letting WbFoundationFlag fall back to legacy.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/AcDream.App/AcDream.App.csproj

@@ -14,6 +14,7 @@
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="Silk.NET.OpenGL" Version="2.23.0" />
+    <PackageReference Include="Silk.NET.OpenGL.Extensions.ARB" Version="2.23.0" />
     <PackageReference Include="Silk.NET.Windowing" Version="2.23.0" />
     <PackageReference Include="Silk.NET.Input" Version="2.23.0" />
     <PackageReference Include="Silk.NET.OpenAL" Version="2.23.0" />

src/AcDream.App/Rendering/Wb/BindlessSupport.cs

@@ -0,0 +1,67 @@
+using Silk.NET.OpenGL;
+using Silk.NET.OpenGL.Extensions.ARB;
+
+namespace AcDream.App.Rendering.Wb;
+
+/// <summary>
+/// Thin wrapper around <see cref="ArbBindlessTexture"/> + capability detection
+/// for the modern rendering path. Constructed once at startup. Throws if the
+/// extension isn't available — callers must check <see cref="IsAvailable"/>
+/// before constructing for production use.
+/// </summary>
+public sealed class BindlessSupport
+{
+    private readonly GL _gl;
+    private readonly ArbBindlessTexture _ext;
+
+    public bool IsAvailable => true;  // Construction succeeded
+
+    public BindlessSupport(GL gl, ArbBindlessTexture extension)
+    {
+        _gl = gl;
+        _ext = extension;
+    }
+
+    public static bool TryCreate(GL gl, out BindlessSupport? support)
+    {
+        if (gl.TryGetExtension<ArbBindlessTexture>(out var ext))
+        {
+            support = new BindlessSupport(gl, ext);
+            return true;
+        }
+        support = null;
+        return false;
+    }
+
+    /// <summary>Get a 64-bit bindless handle for the texture and make it resident.
+    /// Idempotent: handle is the same for a given texture name.</summary>
+    public ulong GetResidentHandle(uint textureName)
+    {
+        ulong h = _ext.GetTextureHandle(textureName);
+        if (!_ext.IsTextureHandleResident(h))
+            _ext.MakeTextureHandleResident(h);
+        return h;
+    }
+
+    /// <summary>Release residency for a handle. Call before deleting the underlying texture.</summary>
+    public void MakeNonResident(ulong handle)
+    {
+        if (_ext.IsTextureHandleResident(handle))
+            _ext.MakeTextureHandleNonResident(handle);
+    }
+
+    /// <summary>Detect <c>GL_ARB_shader_draw_parameters</c> in addition to bindless.
+    /// N.5's vertex shader uses <c>gl_BaseInstanceARB</c> and <c>gl_DrawIDARB</c>
+    /// from this extension.</summary>
+    public bool HasShaderDrawParameters(GL gl)
+    {
+        int n = 0;
+        gl.GetInteger(GLEnum.NumExtensions, out n);
+        for (int i = 0; i < n; i++)
+        {
+            string ext = gl.GetStringS(StringName.Extensions, (uint)i);
+            if (ext == "GL_ARB_shader_draw_parameters") return true;
+        }
+        return false;
+    }
+}