Fix stair approach fall-through and relax steep slope climbing

Relaxed walkable slope threshold from 0.40 to 0.35 (~70° max) for
steeper stair climbing. Tightened WMO floor cache above-tolerance
back to 0.25 units to prevent cached stair landing from overriding
approach floor. Added M2 floor preference for ship decks to prevent
falling through to water below.

src/rendering/camera_controller.cpp

@@ -506,7 +506,7 @@ void CameraController::update(float deltaTime) {
                 groundH = selectReachableFloor(terrainH, wmoH, targetPos.z, stepUpBudget);
             }
 
-            // 2. Multi-sample for M2 objects (rugs, planks, bridges) —
+            // 2. Multi-sample for M2 objects (rugs, planks, bridges, ships) —
             //    these are narrow and need offset probes to detect reliably.
             if (m2Renderer) {
                 constexpr float FOOTPRINT = 0.4f;
@@ -519,9 +519,13 @@ void CameraController::update(float deltaTime) {
                 for (const auto& o : offsets) {
                     auto m2H = m2Renderer->getFloorHeight(
                         targetPos.x + o.x, targetPos.y + o.y, m2ProbeZ);
-                    if (m2H && *m2H <= targetPos.z + stepUpBudget &&
-                        (!groundH || *m2H > *groundH)) {
-                        groundH = m2H;
+                    // Prefer M2 floors (ships, platforms) even if slightly lower than terrain
+                    // to prevent falling through ship decks to water below
+                    if (m2H && *m2H <= targetPos.z + stepUpBudget) {
+                        if (!groundH || *m2H > *groundH ||
+                            (*m2H >= targetPos.z - 0.5f && *groundH < targetPos.z - 1.0f)) {
+                            groundH = m2H;
+                        }
                     }
                 }
             }

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 >= 0.40f);  // ~66° max slope (relaxed for steep stairs)
+        bool isFloor = (absNz >= 0.35f);  // ~70° 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) < 0.40f) continue; // too steep (~66° max slope)
+                    if (std::abs(worldN.z) < 0.35f) continue; // too steep (~70° 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 >= 0.40f);  // ~66° max slope (relaxed for steep stairs)
+        bool isFloor = (absNz >= 0.35f);  // ~70° 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));
@@ -1749,8 +1749,8 @@ std::optional<float> WMORenderer::getFloorHeight(float glX, float glY, float glZ
     if (gridIt != precomputedFloorGrid.end()) {
         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 = 0.50f;   // tune: 0.25–0.60 (increased to catch borderline floors)
+        // Reject cache if it's too high above us (prevents stair landing from overriding approach floor)
+        constexpr float CACHE_ABOVE = 0.25f;   // tight above threshold (prevents stair landing cache hit)
         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 >= 0.40f) continue;
+                    if (absNz >= 0.35f) 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