fix(ui): a picker whose list failed says so, and takes no pick while one is being written

- Combobox gains `error` (said in the list, not "No matches") and a soft `disabled` (keeps the
  focus, announced, opens and changes nothing).
- UserPicker passes both: the share dialog's recipient picker is off while a share is pending, and
  the share and quota pickers say when the user list failed to load.
- ChannelPicker and the Plex playlist/collection pickers say a failed load too.
- The channel menu's Tags row says loading / failed instead of "no tags yet".

frontend/src/components/ChannelPicker.tsx

@@ -40,6 +40,7 @@ export default function ChannelPicker({
       selected={filters.channelIds}
       onChange={(channelIds) => setFilters({ ...filters, channelIds })}
       loading={channelsQuery.isLoading}
+      error={channelsQuery.isError && !channelsQuery.data ? t("common.loadError") : undefined}
       emptyText={t("sidebar.noChannelMatch")}
       selectedLabels={selectedLabels}
     />

frontend/src/components/Channels.tsx

@@ -329,6 +329,7 @@ export default function Channels() {
     onView,
     onOpenWizard,
     tags: userTags,
+    tagsState: tagsQuery.isPending ? "loading" : tagsQuery.isError ? "error" : "ready",
     onToggleTag: (c, tagId) => toggleTag(c.id, tagId, c.tag_ids.includes(tagId)),
     onPickPriority: pickPriority,
   });

frontend/src/components/PlexSidebar.tsx

@@ -371,6 +371,8 @@ function PlaylistPicker() {
       query={query}
       onQueryChange={setQuery}
       placeholder={t("plex.playlist.pickerPlaceholder")}
+      loading={playlistsQ.isLoading}
+      error={playlistsQ.isError && !playlistsQ.data ? t("common.loadError") : undefined}
       emptyText={t("plex.playlist.none")}
       renderOption={(o) =>
         o.value === CREATE_PLAYLIST ? (
@@ -454,6 +456,7 @@ function CollectionPicker({
         onQueryChange={setSearch}
         onOpenChange={setOpen}
         loading={q.isFetching}
+        error={q.isError ? t("common.loadError") : undefined}
         placeholder={t("plex.filter.collectionSearch")}
         emptyText={t("plex.filter.collectionEmpty")}
         onChange={(next) => {

frontend/src/components/ShareDialog.tsx

@@ -46,6 +46,8 @@ function UserShare({ job }: { job: DownloadJob }) {
       <UserPicker
         users={list}
         loading={recipients.isLoading}
+        error={recipients.isError}
+        disabled={share.isPending}
         onPick={(u) => {
           if (!share.isPending) share.mutate(u.email);
         }}

frontend/src/components/UserPicker.tsx

@@ -1,3 +1,4 @@
+import { useTranslation } from "react-i18next";
 import Combobox from "./ui/Combobox";
 
 // Pick one registered user by name or email: the download quota's "any user" picker and the share
@@ -17,13 +18,20 @@ export default function UserPicker<U extends PickableUser>({
   label,
   placeholder,
   loading,
+  error,
+  disabled,
 }: {
   users: readonly U[];
   onPick: (u: U) => void;
   label: string;
   placeholder: string;
   loading?: boolean;
+  /** The user list failed to load: the picker says so instead of "No matches". */
+  error?: boolean;
+  /** The last pick is still being acted on: no second one meanwhile. */
+  disabled?: boolean;
 }) {
+  const { t } = useTranslation();
   const byId = new Map(users.map((u) => [String(u.id), u]));
   return (
     <Combobox
@@ -31,6 +39,8 @@ export default function UserPicker<U extends PickableUser>({
       placeholder={placeholder}
       multiple={false}
       loading={loading}
+      error={error ? t("common.loadError") : undefined}
+      disabled={disabled}
       selected={[]}
       // The label carries both, so the client filter matches a name OR an email.
       options={users.map((u) => ({

frontend/src/components/downloadAdmin.tsx

@@ -149,6 +149,7 @@ function QuotaUserPicker({ onPick }: { onPick: (u: { id: number; email: string }
       <UserPicker
         users={list}
         loading={users.isLoading}
+        error={users.isError}
         onPick={(u) => onPick({ id: u.id, email: u.email })}
         label={t("downloads.admin.quotaPickPlaceholder")}
         placeholder={t("downloads.admin.quotaPickPlaceholder")}

frontend/src/components/ui/Combobox.dom.test.tsx

@@ -276,6 +276,33 @@ describe("Combobox", () => {
 // PageUp/PageDown (E11, owner request): the sidebar's channel filter and the Plex pickers run to
 // hundreds of rows, and floating-ui's list navigation has only the arrows. jsdom has no layout, so a
 // page is the fixed fallback of 10 rows; the measured page is pinned in lib/listPaging.
+// E28 review J1 + J2: a failed list said "No matches" (an error dressed as an empty result), and a
+// picker whose pick was still being written took another pick.
+describe("Combobox · honest states", () => {
+  it("says the list failed to load, not that nothing matched", () => {
+    wrap(
+      <Combobox label="User" options={[]} selected={[]} onChange={vi.fn()} error="Load failed" />,
+    );
+    fireEvent.focus(screen.getByRole("combobox"));
+    expect(screen.getByText("Load failed")).toBeTruthy();
+    expect(screen.queryByText("common.noResults")).toBeNull();
+  });
+
+  it("disabled: keeps the focus, opens nothing and picks nothing", () => {
+    const onChange = vi.fn();
+    wrap(<Combobox label="Genre" options={OPTIONS} selected={[]} onChange={onChange} disabled />);
+    const field = screen.getByRole("combobox");
+    field.focus();
+    fireEvent.focus(field);
+    expect(screen.queryByRole("option", { hidden: true })).toBeNull();
+    fireEvent.keyDown(field, { key: "ArrowDown" });
+    fireEvent.keyDown(field, { key: "Enter" });
+    expect(onChange).not.toHaveBeenCalled();
+    expect(field.getAttribute("aria-disabled")).toBe("true");
+    expect(document.activeElement).toBe(field); // not natively disabled: the focus stays put
+  });
+});
+
 describe("Combobox · paging", () => {
   const rows = (disabled: number[] = []) =>
     Array.from({ length: 25 }, (_, i) => ({ value: `Row ${i}`, disabled: disabled.includes(i) }));

frontend/src/components/ui/Combobox.tsx

@@ -52,6 +52,12 @@ export interface ComboboxProps {
    *  the list server-side (then `options` arrives pre-filtered). */
   clientFilter?: boolean;
   loading?: boolean;
+  /** The options failed to load: said in the list instead of "No matches" (an error is not an empty
+   *  result — E28 review J1). */
+  error?: string;
+  /** Takes no pick (e.g. the last one is still being written, J2). Soft, like `FocusSafeButton`: the
+   *  field keeps the focus (a natively disabled one drops it to <body>), announced as unavailable. */
+  disabled?: boolean;
   /** Shown when there are no options to list. */
   emptyText?: string;
   /** Cap on rendered rows for a huge vocabulary; the rest hide behind the search. Default 50. */
@@ -75,6 +81,8 @@ export default function Combobox({
   onQueryChange,
   clientFilter = true,
   loading = false,
+  error,
+  disabled = false,
   emptyText,
   maxVisible = 50,
   renderOption,
@@ -102,6 +110,7 @@ export default function Combobox({
   const labelFor = (v: string) => selectedLabels?.[v] ?? labelCache.current[v] ?? v;
 
   const setOpenAnd = (next: boolean) => {
+    if (next && disabled) return;
     setOpen(next);
     onOpenChange?.(next);
     // Closing discards the typed query: the list is for "find and pick", and a leftover filter would
@@ -145,6 +154,7 @@ export default function Combobox({
   const hiddenCount = filtered.length - visible.length;
 
   const commit = (value: string) => {
+    if (disabled) return;
     if (multiple) {
       onChange(
         selected.includes(value) ? selected.filter((x) => x !== value) : [...selected, value],
@@ -183,13 +193,14 @@ export default function Combobox({
         className={clsx(
           fieldClass({ size: "free" }),
           "flex min-h-8 w-full cursor-text flex-wrap items-center gap-1 px-1.5 py-0.5 text-sm",
+          disabled && "cursor-not-allowed opacity-50",
         )}
       >
         {selected.map((v) => (
           <DismissibleChip
             key={v}
             className="max-w-40"
-            onDismiss={() => onChange(selected.filter((x) => x !== v))}
+            onDismiss={() => !disabled && onChange(selected.filter((x) => x !== v))}
             dismissLabel={t("common.removeNamed", { name: labelFor(v) })}
           >
             {labelFor(v)}
@@ -209,13 +220,20 @@ export default function Combobox({
               if (e.key === "Enter" && open && idx != null && visible[idx]) {
                 e.preventDefault(); // select the highlighted option, don't submit a surrounding form
                 if (!visible[idx].disabled) commit(visible[idx].value);
-              } else if (e.key === "Backspace" && query === "" && selected.length > 0) {
+              } else if (
+                e.key === "Backspace" &&
+                !disabled &&
+                query === "" &&
+                selected.length > 0
+              ) {
                 // Backspace on an empty field removes the last chip (react-select behaviour).
                 onChange(selected.slice(0, -1));
               }
             },
           })}
           value={query}
+          readOnly={disabled}
+          aria-disabled={disabled || undefined}
           aria-label={label}
           placeholder={
             selected.length === 0
@@ -237,7 +255,11 @@ export default function Combobox({
       >
         {/* The scroll box owns the height cap AND the scroll-fade mask (ref+style on the same element). */}
         <div ref={fade.ref} style={fade.style} className="max-h-64 overflow-y-auto no-scrollbar">
-          {loading && filtered.length === 0 ? (
+          {error && filtered.length === 0 ? (
+            <p role="alert" className="px-2 py-1.5 text-xs text-danger">
+              {error}
+            </p>
+          ) : loading && filtered.length === 0 ? (
             <p className="px-2 py-1.5 text-xs text-muted">{t("common.loading")}</p>
           ) : filtered.length === 0 ? (
             <p className="px-2 py-1.5 text-xs text-muted">

frontend/src/components/useChannelActions.dom.test.tsx

@@ -40,6 +40,7 @@ afterEach(() => {
   h.role = "user";
   h.canWrite = true;
   tags = [];
+  tagsState = "ready";
   onToggleTag.mockReset();
   onPickPriority.mockReset();
 });
@@ -70,6 +71,7 @@ const onView = vi.fn();
 const onToggleTag = vi.fn();
 const onPickPriority = vi.fn();
 let tags: Tag[] = [];
+let tagsState: "loading" | "error" | "ready" = "ready";
 const tag = (id: number, name: string) => ({ id, name }) as Tag;
 function mount() {
   const qc = new QueryClient({ defaultOptions: { mutations: { retry: false } } });
@@ -77,7 +79,15 @@ function mount() {
     <QueryClientProvider client={qc}>{children}</QueryClientProvider>
   );
   return renderHook(
-    () => useChannelActions({ onView, onOpenWizard: () => {}, tags, onToggleTag, onPickPriority }),
+    () =>
+      useChannelActions({
+        onView,
+        onOpenWizard: () => {},
+        tags,
+        tagsState,
+        onToggleTag,
+        onPickPriority,
+      }),
     { wrapper },
   );
 }
@@ -220,6 +230,14 @@ describe("useChannelActions — the Tags submenu", () => {
     expect(onToggleTag).toHaveBeenCalledWith(expect.objectContaining({ id: "UC1" }), 2);
   });
 
+  // E28 review J3: a failed /tags read said "no tags yet" — an error dressed as an empty list.
+  it("says the tags are loading, or failed to load, instead of 'no tags yet'", () => {
+    tagsState = "loading";
+    expect(row(ch(), "tags")).toMatchObject({ disabled: true, note: "common.loading" });
+    tagsState = "error";
+    expect(row(ch(), "tags")).toMatchObject({ disabled: true, note: "common.loadError" });
+  });
+
   it("stays in place, off, saying where tags are made, with no tag yet", () => {
     expect(row(ch(), "tags")).toMatchObject({ disabled: true, note: "channels.row.noTagsYet" });
     expect(row(ch(), "tags").items).toBeUndefined();

frontend/src/components/useChannelActions.tsx

@@ -23,6 +23,7 @@ export function useChannelActions({
   onView,
   onOpenWizard,
   tags,
+  tagsState = "ready",
   onToggleTag,
   onPickPriority,
 }: {
@@ -30,6 +31,9 @@ export function useChannelActions({
   onOpenWizard: () => void;
   /** The reader's own tags (no system tags) — the Tags submenu lists them A–Z. */
   tags: readonly Tag[];
+  /** Whether `tags` is the answer yet: loading or failed is said as such, never as "no tags yet"
+   *  (E28 review J3). */
+  tagsState?: "loading" | "error" | "ready";
   onToggleTag: (c: ManagedChannel, tagId: number) => void;
   /** A priority step picked: the caller re-sorts its list and follows the row. */
   onPickPriority: (c: ManagedChannel, priority: number) => void;
@@ -149,8 +153,15 @@ export function useChannelActions({
       label: t("channels.tags.label"),
       icon: <Tags className="w-4 h-4" />,
     };
-    if (tags.length === 0)
-      return { ...base, disabled: true, note: t("channels.row.noTagsYet"), onSelect: () => {} };
+    if (tags.length === 0) {
+      const note =
+        tagsState === "loading"
+          ? t("common.loading")
+          : tagsState === "error"
+            ? t("common.loadError")
+            : t("channels.row.noTagsYet");
+      return { ...base, disabled: true, note, onSelect: () => {} };
+    }
     const on = new Set(c.tag_ids);
     return {
       ...base,