3D viewer: non-blocking STEP parse in Web Worker, loading progress bar, data overlay (file size + triangle count), finer tessellation + flat shading

theme/blog_share_theme.css

@@ -810,6 +810,7 @@ html.theme-light #content code {
 
 /* ---------- 3D model viewer (STL / STEP) ---------- */
 .model-viewer {
+    position: relative;
     margin: 1em 0;
     background: #1d2021;
     border: 1px solid var(--background-highlight);
@@ -817,6 +818,22 @@ html.theme-light #content code {
     overflow: hidden;
 }
 
+.model-viewer-data {
+    position: absolute;
+    top: 8px;
+    right: 10px;
+    z-index: 3;
+    display: none;
+    font-size: 0.75em;
+    color: #a89984;
+    background: rgba(40, 40, 40, 0.8);
+    border: 1px solid #504945;
+    border-radius: 6px;
+    padding: 2px 10px;
+    font-variant-numeric: tabular-nums;
+    pointer-events: none;
+}
+
 .model-viewer-canvas {
     position: relative;
 }
@@ -832,6 +849,33 @@ html.theme-light #content code {
     color: #fb4934;
 }
 
+.model-viewer-progress {
+    position: relative;
+    height: 6px;
+    margin: 0 48px 22px;
+    background: #3c3836;
+    border-radius: 3px;
+    overflow: hidden;
+}
+
+.model-viewer-progress-fill {
+    height: 100%;
+    width: 0;
+    background: #b8bb26;
+    border-radius: 3px;
+    transition: width 150ms ease;
+}
+
+.model-viewer-progress-fill.indeterminate {
+    width: 40%;
+    animation: model-progress 1.1s ease-in-out infinite;
+}
+
+@keyframes model-progress {
+    0% { transform: translateX(-100%); }
+    100% { transform: translateX(250%); }
+}
+
 .model-viewer-hint {
     position: absolute;
     top: 8px;