Relax walkable slope threshold and floor cache for steep stairs

Changed walkable slope threshold from 0.45 (63°) to 0.40 (66°) in both
WMO and M2 collision to allow climbing steeper stairs (like 60° steps).
Increased WMO floor cache above-tolerance from 0.35 to 0.50 units to
prevent falling through floors in places like Booty Bay where cached
floor is slightly above query point.

src/rendering/m2_renderer.cpp

@@ -718,7 +718,7 @@ void M2ModelGPU::CollisionMesh::build() {
         glm::vec3 normal = glm::cross(v1 - v0, v2 - v0);
         float normalLen = glm::length(normal);
         float absNz = (normalLen > 0.001f) ? std::abs(normal.z / normalLen) : 0.0f;
-        bool isFloor = (absNz >= 0.45f);
+        bool isFloor = (absNz >= 0.40f);  // ~66° max slope (relaxed for steep stairs)
         bool isWall  = (absNz < 0.65f);
 
         float triMinX = std::min({v0.x, v1.x, v2.x});
@@ -2573,7 +2573,7 @@ std::optional<float> M2Renderer::getFloorHeight(float glX, float glY, float glZ)
                     if (localN.z < 0.0f) localN = -localN;
                     glm::vec3 worldN = glm::normalize(
                         glm::vec3(instance.modelMatrix * glm::vec4(localN, 0.0f)));
-                    if (std::abs(worldN.z) < 0.45f) continue; // too steep
+                    if (std::abs(worldN.z) < 0.40f) continue; // too steep (~66° max slope)
                 }
 
                 if (hitZ <= localPos.z + 3.0f && hitZ > bestHitZ) {

src/rendering/wmo_renderer.cpp

@@ -1607,7 +1607,7 @@ void WMORenderer::GroupResources::buildCollisionGrid() {
         glm::vec3 normal = glm::cross(edge1, edge2);
         float normalLen = glm::length(normal);
         float absNz = (normalLen > 0.001f) ? std::abs(normal.z / normalLen) : 0.0f;
-        bool isFloor = (absNz >= 0.45f);
+        bool isFloor = (absNz >= 0.40f);  // ~66° max slope (relaxed for steep stairs)
         bool isWall = (absNz < 0.65f);  // Matches walkable slope threshold
 
         int cellMinX = std::max(0, static_cast<int>((triMinX - gridOrigin.x) * invCellW));
@@ -1750,7 +1750,7 @@ std::optional<float> WMORenderer::getFloorHeight(float glX, float glY, float glZ
         float cachedHeight = gridIt->second;
         // Only trust cache if it's basically at foot level.
         // Prevent ledges/shoulder ramps from being treated as "floor".
-        constexpr float CACHE_ABOVE = 0.35f;   // tune: 0.25–0.60
+        constexpr float CACHE_ABOVE = 0.50f;   // tune: 0.25–0.60 (increased to catch borderline floors)
         constexpr float CACHE_BELOW = 4.0f;    // keep generous below
             if (cachedHeight <= glZ + CACHE_ABOVE && cachedHeight >= glZ - CACHE_BELOW) {
             // Persistent cache doesn't store normal — report as flat
@@ -2066,7 +2066,7 @@ bool WMORenderer::checkWallCollision(const glm::vec3& from, const glm::vec3& to,
                 if (horizDist <= PLAYER_RADIUS) {
                     // Skip floor-like surfaces — grounding handles them, not wall collision
                     float absNz = std::abs(normal.z);
-                    if (absNz >= 0.45f) continue;
+                    if (absNz >= 0.40f) continue;
 
                     const float SKIN = 0.005f;        // small separation so we don't re-collide immediately
                     // Stronger push when inside WMO for more responsive indoor collision