Increase lava/magma smoke particle emission rate from 16 to 32 per second

Double the smoke particle emission rate to create visually richer lava and magma
effects. Current implementation emitted only 16 particles/sec per emitter (~88 in
steady state), which appeared sparse especially in multi-emitter lava areas.
Increasing to 32/sec provides denser steam/smoke effects (~176 in steady state)
while remaining well under the 1000 particle cap. This tuning opportunity was
documented in status.md as a known gap in visual completeness.

src/rendering/m2_renderer.cpp

@@ -1997,7 +1997,7 @@ void M2Renderer::update(float deltaTime, const glm::vec3& cameraPos, const glm::
     std::uniform_real_distribution<float> distDrift(-0.2f, 0.2f);
 
     smokeEmitAccum += deltaTime;
-    float emitInterval = 1.0f / 16.0f;  // 16 particles per second per emitter
+    float emitInterval = 1.0f / 32.0f;  // 32 particles per second per emitter (was 16; increased for denser lava/magma effects)
 
     if (smokeEmitAccum >= emitInterval &&
         static_cast<int>(smokeParticles.size()) < MAX_SMOKE_PARTICLES) {