Fix invisible NPC body parts caused by texture alpha

Character fragment shader was using texture alpha, which could be 0 in
baked NPC textures. Force alpha=1 for opaque character rendering.

src/rendering/character_renderer.cpp

@@ -154,7 +154,8 @@ bool CharacterRenderer::initialize() {
             float fogFactor = clamp((uFogEnd - fogDist) / (uFogEnd - uFogStart), 0.0, 1.0);
             result = mix(uFogColor, result, fogFactor);
 
-            FragColor = vec4(result, texColor.a);
+            // Force alpha=1 for opaque character rendering (baked NPC textures may have alpha=0)
+            FragColor = vec4(result, 1.0);
         }
     )";