Add per-group spatial grid for WMO collision and reduce collision call frequency

Build a 2D triangle grid per WMO group at load time so getFloorHeight and
checkWallCollision only test triangles in nearby cells instead of brute-forcing
all triangles. Also reduce sweep steps (12→4), ground probes (3→1), camera
floor probes (5→2), throttle isInsideWMO to every 10 frames, and early-out
wall collision on first hit.

include/rendering/camera_controller.hpp

@@ -133,6 +133,11 @@ 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 isInsideWMO result (throttled to avoid per-frame cost)
+    bool cachedInsideWMO = false;
+    int insideWMOCheckCounter = 0;
+    glm::vec3 lastInsideWMOCheckPos = glm::vec3(0.0f);
+
     // Swimming
     bool swimming = false;
     bool wasSwimming = false;