feat(preview): default inspect mode to roads

scripts/lib/cesium-preview.js

@@ -258,6 +258,8 @@
       const label = document.createElement("label");
       const input = document.createElement("input");
       input.type = "checkbox";
+      // Road observation is the primary workflow. Keep the optional semantic
+      // layers available, but avoid letting buildings obscure the first view.
       input.checked = false;
       input.dataset.assetId = asset.id;
       input.addEventListener("change", async () => {
@@ -347,8 +349,9 @@
           }
           return;
         }
-        model.show = true;
-        if (asset.toggle) asset.toggle.checked = true;
+        const roadFocus = asset.id === "roads";
+        model.show = roadFocus;
+        if (asset.toggle) asset.toggle.checked = roadFocus;
       }));
       if (viewMode !== "inspect") {
         for (const asset of semanticAssets(assets)) {