feat(ui): explain unavailable workspaces

src/trx-client/trx-frontend/trx-frontend-http/assets/web/ui-core.js

@@ -127,8 +127,8 @@
 
   const layouts = {
     compact: { label: "Compact", description: "Essential tuning and audio controls", advanced: false, preferredTab: "main" },
-    broadcast: { label: "Broadcast", description: "WFM, RDS, stereo and interference monitoring", advanced: false, preferredTab: "main", capability: "broadcast" },
+    broadcast: { label: "Broadcast", description: "WFM, RDS, stereo and interference monitoring", unavailable: "Broadcast requires an enumerated WFM-capable receiver", advanced: false, preferredTab: "main", capability: "broadcast" },
-    digital: { label: "Digital", description: "Decoder status, messages and background decoding", advanced: false, preferredTab: "digital-modes", capability: "digital" },
+    digital: { label: "Digital", description: "Decoder status, messages and background decoding", unavailable: "Digital requires a compatible rig mode and an available decoder", advanced: false, preferredTab: "digital-modes", capability: "digital" },
     full: { label: "Full controls", description: "Every control supported by the selected rig", advanced: true, preferredTab: "main" },
   };
   const layoutCapabilities = { broadcast: false, digital: false };
@@ -146,6 +146,17 @@
     return !layout.capability || layoutCapabilities[layout.capability] === true;
   }
 
+  function unavailableLayoutMessage() {
+    const unavailable = Object.values(layouts).filter(layout => !layoutAvailable(layout) && layout.unavailable);
+    return unavailable.length ? `Unavailable: ${unavailable.map(layout => layout.unavailable).join("; ")}.` : "";
+  }
+
+  function updateLayoutDescription(layout) {
+    const description = document.getElementById("operator-layout-description");
+    if (!description) return;
+    description.textContent = [layout.description, unavailableLayoutMessage()].filter(Boolean).join(" · ");
+  }
+
   function refreshLayoutOptions() {
     const select = document.getElementById("operator-layout-select");
     if (!select) return;
@@ -158,6 +169,8 @@
     const available = Array.from(select.options).some(option => option.value === previous);
     select.value = available ? previous : "compact";
     if (!available && previous !== "compact") api.applyLayout("compact", { persist: false });
+    select.title = unavailableLayoutMessage();
+    updateLayoutDescription(layouts[select.value] || layouts.compact);
   }
 
   api.setLayoutCapabilities = function setLayoutCapabilities(capabilities = {}) {
@@ -189,8 +202,7 @@
     if (options.persist !== false) localStorage.setItem(layoutStorageKey(), document.body.dataset.operatorLayout);
     const details = document.getElementById("advanced-radio-controls");
     if (details) details.open = layout.advanced;
-    const description = document.getElementById("operator-layout-description");
+    updateLayoutDescription(layout);
-    if (description) description.textContent = layout.description;
     if (options.navigate && typeof window.navigateToTab === "function") {
       window.navigateToTab(layout.preferredTab);
     }