feat(app): render landblock with height-ramp shader + orbit camera

Adds a 2-stage GLSL shader (vertex + fragment), a Shader helper that
compiles/links and exposes SetMatrix4 for uniforms, and an OrbitCamera
with yaw/pitch/distance and a 192-unit-centered target for a single
landblock. TerrainRenderer now takes a Shader and issues an actual
DrawElements call with uView + uProjection uniforms. GameWindow owns
the Shader and Camera, routes mouse drag to camera yaw/pitch, and
scroll wheel to camera distance.

The fragment shader maps world Z to a green-brown-white ramp so
lowlands read green, midlands brown, and peaks white — no textures
yet, but enough to visually confirm the terrain shape.

Shaders are copied to the output dir via a <None Update> item group.

Smoke verified against real dats: process stays alive with no GL
errors, no shader compile/link failures, and no exception trail.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/AcDream.App/AcDream.App.csproj

@@ -19,4 +19,9 @@
   <ItemGroup>
     <ProjectReference Include="..\AcDream.Core\AcDream.Core.csproj" />
   </ItemGroup>
+  <ItemGroup>
+    <None Update="Rendering\Shaders\*.*">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+  </ItemGroup>
 </Project>