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>
