Optimize collision further: skip when stationary, cache floor height, fix drop bug

- Skip wall collision sweep entirely when player isn't moving (saves all
  collision calls when standing still)
- Reduce max sweep steps from 4 to 2 with 1.0f step size (all paths:
  follow, free-fly, swimming)
- Cache floor height between frames, reuse when position changes <0.5 units
- Fix floor height not updating after walking off tall objects (fountain etc)
  by always smoothing toward detected ground instead of ignoring drops >2 units
- Reduce free-fly ground probes from 5 to 1
- Disable WMO camera collision (raycast + floor probes) for performance
- Add spatial grid to raycastBoundingBoxes for when camera collision is re-enabled

include/rendering/camera_controller.hpp

@@ -4,6 +4,7 @@
 #include "core/input.hpp"
 #include <SDL2/SDL.h>
 #include <functional>
+#include <optional>
 
 namespace wowee {
 namespace rendering {
@@ -133,6 +134,10 @@ private:
     static constexpr float JUMP_BUFFER_TIME = 0.15f;  // 150ms input buffer
     static constexpr float COYOTE_TIME = 0.10f;        // 100ms grace after leaving ground
 
+    // Cached floor height between frames (skip expensive probes when barely moving)
+    std::optional<float> cachedFloorHeight;
+    glm::vec2 cachedFloorPos = glm::vec2(0.0f);
+
     // Cached isInsideWMO result (throttled to avoid per-frame cost)
     bool cachedInsideWMO = false;
     int insideWMOCheckCounter = 0;