Soften WMO wall pushback and fix fountain climbing

Cap WMO swept wall collision pushback to 0.15 units (was 0.55) so walls
stop the player without violent shoves. Fix M2 stepped fountain lateral
push using effectiveTop instead of rawMax.z so the near-top check matches
the stepped profile height at the player's radial position.

src/rendering/m2_renderer.cpp

@@ -2544,7 +2544,7 @@ bool M2Renderer::checkCollision(const glm::vec3& from, const glm::vec3& to,
         if (allowEscapeRelax) {
             continue;
         }
-        if (stepableLowObject && localFrom.z >= rawMax.z - 0.35f) {
+        if (stepableLowObject && localFrom.z >= effectiveTop - 0.35f) {
             // Already on/near top surface: don't apply lateral push that ejects
             // the player from the object (carpets, platforms, etc).
             continue;