Implement FSR 2.2 temporal upscaling

Full FSR 2.2 pipeline with depth-based motion vector reprojection,
temporal accumulation with YCoCg neighborhood clamping, and RCAS
contrast-adaptive sharpening.

Architecture (designed for FSR 3.x frame generation readiness):
- Camera: Halton(2,3) sub-pixel jitter with unjittered projection
  stored separately for motion vector computation
- Motion vectors: compute shader reconstructs world position from
  depth + inverse VP, reprojects with previous frame's VP
- Temporal accumulation: compute shader blends 5-10% current frame
  with 90-95% clamped history, adaptive blend for disocclusion
- History: ping-pong R16G16B16A16 buffers at display resolution
- Sharpening: RCAS fragment pass with contrast-adaptive weights

Integration:
- FSR2 replaces both FSR1 and MSAA when enabled
- Scene renders to internal resolution framebuffer (no MSAA)
- Compute passes run between scene and swapchain render passes
- Camera cut detection resets history on teleport
- Quality presets shared with FSR1 (0.50-0.77 scale factors)
- UI: "Upscaling" combo with Off/FSR 1.0/FSR 2.2 options

src/rendering/camera.cpp

@@ -20,6 +20,13 @@ void Camera::updateProjectionMatrix() {
     projectionMatrix = glm::perspective(glm::radians(fov), aspectRatio, nearPlane, farPlane);
     // Vulkan clip-space has Y pointing down; flip the projection's Y axis.
     projectionMatrix[1][1] *= -1.0f;
+    unjitteredProjectionMatrix = projectionMatrix;
+
+    // Re-apply jitter if active
+    if (jitterOffset.x != 0.0f || jitterOffset.y != 0.0f) {
+        projectionMatrix[2][0] += jitterOffset.x;
+        projectionMatrix[2][1] += jitterOffset.y;
+    }
 }
 
 glm::vec3 Camera::getForward() const {
@@ -40,6 +47,21 @@ glm::vec3 Camera::getUp() const {
     return glm::normalize(glm::cross(getRight(), getForward()));
 }
 
+void Camera::setJitter(float jx, float jy) {
+    // Remove old jitter, apply new
+    projectionMatrix[2][0] -= jitterOffset.x;
+    projectionMatrix[2][1] -= jitterOffset.y;
+    jitterOffset = glm::vec2(jx, jy);
+    projectionMatrix[2][0] += jitterOffset.x;
+    projectionMatrix[2][1] += jitterOffset.y;
+}
+
+void Camera::clearJitter() {
+    projectionMatrix[2][0] -= jitterOffset.x;
+    projectionMatrix[2][1] -= jitterOffset.y;
+    jitterOffset = glm::vec2(0.0f);
+}
+
 Ray Camera::screenToWorldRay(float screenX, float screenY, float screenW, float screenH) const {
     float ndcX = (2.0f * screenX / screenW) - 1.0f;
     // Vulkan Y-flip is baked into projectionMatrix, so NDC Y maps directly: