feat(channels): an Added column, and About cards that wait for a resting pointer

The channel manager lists when each follow reached the list (the
subscription import that first saw it, or a subscribe made here) as a
sortable Added date after Last upload. The About cell's card opens after the
pointer rests on it for half a second instead of at once, and a scroll puts
an open one away.

frontend/src/i18n/locales/en/channels.json

@@ -82,6 +82,7 @@
     "stored": "Stored",
     "subs": "Subscribers",
     "lastUpload": "Last upload",
+    "added": "Added",
     "length": "Length",
     "tags": "Tags",
     "actions": "Actions"

frontend/src/i18n/locales/hu/channels.json

@@ -82,6 +82,7 @@
     "stored": "Tárolt",
     "subs": "Feliratkozók",
     "lastUpload": "Utolsó feltöltés",
+    "added": "Hozzáadva",
     "length": "Hossz",
     "tags": "Címkék",
     "actions": "Műveletek"

frontend/src/lib/api/channels.ts

@@ -73,6 +73,9 @@ export interface ManagedChannel {
   description: string | null;
   stored_videos: number;
   last_video_at: string | null;
+  /** When the follow reached this list: the subscription import that first saw it, or a
+   *  subscribe made here. */
+  added_at: string;
   total_duration_seconds: number;
   priority: number;
   hidden: boolean;

frontend/src/modules/channels/AboutCell.dom.test.tsx

@@ -0,0 +1,69 @@
+// @vitest-environment jsdom
+//
+// The About cell's card opened the instant a pointer crossed the cell, so scrolling the table over
+// a column of them popped card after card. It waits for the pointer to rest on the cell now, and a
+// scroll puts an open one away.
+import { describe, it, expect, vi, afterEach, beforeEach } from "vitest";
+import { render, screen, fireEvent, act, cleanup } from "@testing-library/react";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+
+import AboutCell from "./AboutCell";
+import { api } from "../../lib/api";
+
+beforeEach(() => {
+  vi.useFakeTimers();
+  vi.spyOn(api, "channelDetail").mockReturnValue(new Promise(() => {}));
+});
+afterEach(() => {
+  cleanup();
+  vi.useRealTimers();
+  vi.restoreAllMocks();
+});
+
+function mount() {
+  const qc = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+  render(
+    <QueryClientProvider client={qc}>
+      <AboutCell text="An element of truth" channelId="UC1" />
+    </QueryClientProvider>,
+  );
+  return screen.getByText("An element of truth");
+}
+// Present in the DOM is enough: it paints once floating-ui has placed it, which a fake clock never lets happen.
+const card = () => document.querySelector('[role="tooltip"]');
+const wait = (ms: number) => act(() => vi.advanceTimersByTime(ms));
+const enter = (el: HTMLElement) =>
+  act(() => {
+    fireEvent.pointerEnter(el);
+    fireEvent.mouseEnter(el);
+    fireEvent.mouseMove(el);
+  });
+
+describe("AboutCell — the hover card", () => {
+  it("does not open for a pointer passing over the cell", async () => {
+    const cell = mount();
+    enter(cell);
+    await wait(300);
+    expect(card()).toBeNull();
+    fireEvent.mouseLeave(cell);
+    await wait(600);
+    expect(card()).toBeNull();
+  });
+
+  it("opens once the pointer rests on it", async () => {
+    const cell = mount();
+    enter(cell);
+    await wait(550);
+    expect(card()).not.toBeNull();
+  });
+
+  it("goes away when the table scrolls", async () => {
+    const cell = mount();
+    enter(cell);
+    await wait(550);
+    expect(card()).not.toBeNull();
+    act(() => void window.dispatchEvent(new Event("scroll")));
+    await wait(50);
+    expect(card()).toBeNull();
+  });
+});

frontend/src/modules/channels/AboutCell.tsx

@@ -19,6 +19,9 @@ import { SURFACE } from "../../components/ui/surfaces";
  * The card keeps the platform's default hover role (`tooltip`); making this rich, interactive panel
  * properly keyboard-reachable belongs to the focus/a11y work, not to the mechanical migration.
  */
+// How long the pointer rests on a cell before its card opens.
+const ABOUT_REST_MS = 500;
+
 export default function AboutCell({ text, channelId }: { text: string | null; channelId: string }) {
   const preview = (text ?? "").trim();
   const [open, setOpen] = useState(false);
@@ -28,8 +31,11 @@ export default function AboutCell({ text, channelId }: { text: string | null; ch
     onOpenChange: setOpen,
     mode: "hover",
     offset: 6,
-    // Pop instantly like the old cell did; the close grace lets the cursor reach the card.
-    hoverDelay: { open: 0, close: 160 },
+    // Opens once the pointer rests on the cell, not as it crosses one: scrolling the table under a
+    // still pointer, or moving down the column, used to pop card after card. The close grace lets
+    // the cursor reach the card; a scroll puts an open one away.
+    hoverDelay: { open: ABOUT_REST_MS, close: 160 },
+    dismissOnScroll: true,
     // Cap the panel to the space between the trigger and the viewport edge (publishes --fit-max-h) so a
     // long About never runs its top off-screen — at high browser zoom the short viewport made a fixed
     // max-height overflow above the top edge, where the scroll container can't reach.

frontend/src/modules/channels/channelColumns.dom.test.tsx

@@ -13,6 +13,8 @@ import {
 } from "./channelColumns";
 import { NO_TAG_SENTINEL, type ManagedChannel, type Tag } from "../../lib/api";
 import type { TFunction } from "i18next";
+import { render, screen } from "@testing-library/react";
+import { formatDate } from "../../lib/format";
 
 const ch = (over: Partial<ManagedChannel>): ManagedChannel => ({
   id: "c",
@@ -24,6 +26,7 @@ const ch = (over: Partial<ManagedChannel>): ManagedChannel => ({
   description: null,
   stored_videos: 0,
   last_video_at: null,
+  added_at: "2026-06-10T08:00:00+00:00",
   total_duration_seconds: 0,
   priority: 0,
   hidden: false,
@@ -147,3 +150,39 @@ describe("buildChannelColumns — the row's end", () => {
     expect(cols[cols.length - 1]!.render(ch({ id: "UCz" }))).toBe("more:UCz");
   });
 });
+
+describe("buildChannelColumns — Added", () => {
+  const noop = () => {};
+  const cols = buildChannelColumns({
+    t: ((k: string) => k) as never,
+    lang: "en",
+    prioOptions: [],
+    userTags: [],
+    bumpPriority: noop,
+    setPriority: noop,
+    more: () => null,
+    onView: noop,
+    toggleTag: noop,
+    createAndAttachTag: noop,
+    onFilterByTag: noop,
+    suggestionsFor: () => [],
+    onAcceptSuggestion: noop,
+    onDismissSuggestion: noop,
+  });
+  const added = cols.find((c) => c.key === "added");
+
+  it("follows Last upload, and sorts by when the follow reached the list", () => {
+    expect(added?.header).toBe("channels.cols.added");
+    const keys = cols.map((c) => c.key);
+    expect(keys.indexOf("added")).toBe(keys.indexOf("lastUpload") + 1);
+    expect(added?.sortable).toBe(true);
+    const early = ch({ added_at: "2026-06-10T08:00:00+00:00" });
+    const late = ch({ added_at: "2026-10-12T08:00:00+00:00" });
+    expect(added!.sortValue!(late) as number).toBeGreaterThan(added!.sortValue!(early) as number);
+  });
+
+  it("shows the day, not a relative time", () => {
+    render(<>{added!.render(ch({ added_at: "2026-10-12T08:00:00+00:00" }))}</>);
+    expect(screen.getByText(formatDate("2026-10-12T08:00:00+00:00", "en"))).toBeTruthy();
+  });
+});

frontend/src/modules/channels/channelColumns.tsx

@@ -2,7 +2,7 @@ import type { ComponentProps, ReactNode } from "react";
 import type { TFunction } from "i18next";
 import { NO_TAG_SENTINEL, type ManagedChannel, type Tag } from "../../lib/api";
 import { tagPickLabel, type TagList } from "../../lib/tagPicks";
-import { formatCountOrDash, formatTotalHours } from "../../lib/format";
+import { formatCountOrDash, formatDate, formatTotalHours } from "../../lib/format";
 import type { Column } from "../../components/ui/DataTable";
 import { PriorityStepper } from "../../components/ui/PriorityStepper";
 import ChannelLink from "./ChannelLink";
@@ -204,6 +204,20 @@ export function buildChannelColumns(deps: ChannelColumnDeps): Column<ManagedChan
       sortValue: (c) => (c.last_video_at ? new Date(c.last_video_at).getTime() : 0),
       render: (c) => <RelativeTime at={c.last_video_at} empty="—" className="text-muted" />,
     },
+    {
+      key: "added",
+      header: t("channels.cols.added"),
+      nowrap: true,
+      // The day, not a relative time: beside Last upload two "… ago" columns read as one, and when
+      // a channel was added is a fixed fact. Room for "2026. okt. 12." and a sort arrow.
+      width: "7.5rem",
+      tabletHidden: true,
+      sortable: true,
+      sortValue: (c) => new Date(c.added_at).getTime(),
+      render: (c) => (
+        <span className="text-muted tabular-nums">{formatDate(c.added_at, lang)}</span>
+      ),
+    },
     {
       key: "length",
       header: t("channels.cols.length"),

frontend/src/modules/channels/useChannelActions.dom.test.tsx

@@ -59,6 +59,7 @@ const ch = (over: Partial<ManagedChannel> = {}): ManagedChannel => ({
   description: null,
   stored_videos: 0,
   last_video_at: null,
+  added_at: "2026-06-10T08:00:00+00:00",
   total_duration_seconds: 0,
   priority: 0,
   hidden: false,