feat(postbox): enforce unified inbox separation

webui/src/features/postbox/PostboxInboxWidget.tsx

@@ -29,17 +29,22 @@ export default function PostboxInboxWidget({
   const maxItems = numberSetting(configuration.maxItems, 5, 1, 12);
   const load = useCallback(async () => {
     const postboxes = await listPostboxes(settings);
-    if (!postboxes.length) {
-      return { messages: [], total: 0 };
+    const eligible = postboxes.filter(
+      (postbox) => postbox.grouping_policy.mode === "allow"
+    );
+    const separatedCount = postboxes.length - eligible.length;
+    if (!eligible.length) {
+      return { messages: [], total: 0, separatedCount };
     }
-    return listPostboxMessages(
+    const response = await listPostboxMessages(
       settings,
-      postboxes.map((postbox) => postbox.id),
+      eligible.map((postbox) => postbox.id),
       maxItems,
       0,
       "",
       "unread"
     );
+    return { ...response, separatedCount };
   }, [maxItems, settings]);
   const { data, loading, error } = useDashboardWidgetData(load, refreshKey);
 
@@ -50,6 +55,11 @@ export default function PostboxInboxWidget({
           {error}
         </DismissibleAlert>
       )}
+      {data?.separatedCount ? (
+        <DismissibleAlert tone="info" dismissible={false}>
+          {data.separatedCount} governed Postbox source{data.separatedCount === 1 ? " is" : "s are"} shown only in separated inbox views.
+        </DismissibleAlert>
+      ) : null}
       <DashboardWidgetList
         emptyText="No unread Postbox messages."
         items={(data?.messages ?? []).map((message) => ({