Add VBO draw diagnostics for sky rendering debugging

Log first N VBO draws per frame to track shader pipeline, render pass state,
and modelview matrix values during sky rendering. Also log when draws are
skipped due to missing render pass, which helps identify pipeline gaps
where sky geometry is silently dropped.

Author: SPGesus

src/main/java/net/vulkanmod/render/VBO.java

@@ -31,6 +31,10 @@ public class VBO {
 
     private boolean autoIndexed = false;
 
+    // Sky rendering diagnostics — log first N VBO draws per frame
+    private static int skyLogCount = 0;
+    private static final int SKY_LOG_MAX = 30; // total draws to log across all frames
+
     public VBO() {}
 
     public void upload(MeshData meshData) {
@@ -122,6 +126,28 @@ public void drawWithShader(Matrix4f MV, Matrix4f P, ShaderInstance shader) {
             ((ShaderMixed) shader).updateUniformsOnly();
 
             GraphicsPipeline pipeline = ((ShaderMixed) shader).getPipeline();
+
+            // Diagnostic: log VBO draws to track sky rendering
+            if (skyLogCount < SKY_LOG_MAX) {
+                skyLogCount++;
+                String shaderClass = shader.getClass().getSimpleName();
+                String shaderName = "?";
+                try { shaderName = shader.getName(); } catch (Exception ignored) {}
+                boolean pipelineNull = (pipeline == null);
+                Renderer r = Renderer.getInstance();
+                boolean renderPassNull = (r.getBoundRenderPass() == null);
+                // MV matrix: col0.x, col1.y indicate camera rotation (should NOT be 1,1 for rotated camera)
+                float mv00 = MV.m00(), mv11 = MV.m11(), mv01 = MV.m01(), mv10 = MV.m10();
+                org.slf4j.LoggerFactory.getLogger("VBO").info(
+                    "[VBO_DRAW] #{} shader={} class={} pipeline={} renderPass={} idxCnt={} MV[00={} 11={} 01={} 10={}]",
+                    skyLogCount, shaderName, shaderClass,
+                    pipelineNull ? "NULL" : "OK",
+                    renderPassNull ? "NULL" : "OK",
+                    this.indexCount,
+                    String.format("%.3f", mv00), String.format("%.3f", mv11),
+                    String.format("%.3f", mv01), String.format("%.3f", mv10));
+            }
+
             if (pipeline == null) {
                 RenderSystem.getModelViewMatrix().set(savedMV);
                 return;
@@ -138,7 +164,13 @@ public void drawWithShader(Matrix4f MV, Matrix4f P, GraphicsPipeline pipeline) {
             RenderSystem.assertOnRenderThread();
 
             Renderer renderer = Renderer.getInstance();
-            if (renderer.getBoundRenderPass() == null) return;
+            if (renderer.getBoundRenderPass() == null) {
+                if (skyLogCount <= SKY_LOG_MAX) {
+                    org.slf4j.LoggerFactory.getLogger("VBO").warn(
+                        "[VBO_DRAW] SKIPPED draw (no render pass) pipeline={}", pipeline);
+                }
+                return;
+            }
 
             VRenderSystem.applyMVP(MV, P);