fix(clip): clip mode keeps its range, its focus and its keys through the player's own moves

- A mark on the very end seeks a moment short of it; while a clip is marked the end of the item
  neither closes the player nor steps the queue, and Plex's auto-skip waits.
- Plex: Escape and Back peel what is over the picture (info, up-next, the countdown) before the
  clip; Back under a dialog is the dialog's; no range opens while the length is unknown.
- YouTube: the focus goes back to the scissors the user can see, else the player; the panel keeps
  its name, Loop and focus when the view is maximised or restored under it.
- A typed time stays in its field until taken, then shows where it landed; unreadable stays marked
  invalid; a decimal comma is read (ui/TimecodeField, the editor's fields too).
- RangeTrack: a drag is its pointer's, a cancelled drag reports final, an adornment sits beside the
  slider, a caller-chosen focus ring (amber on the clip strip). CropFrame: a drag is its pointer's.
- The editor's remove-cut is a real button at the cut's foot; a segment's keep toggle sits over the
  cut's hit area.

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

@@ -49,6 +49,7 @@ function Harness({
   onClose = () => {},
   onPlayFrom = () => {},
   onSeek = () => {},
+  duration = 3600,
 }: {
   src?: ClipSource;
   start?: ClipRange;
@@ -56,6 +57,7 @@ function Harness({
   onClose?: () => void;
   onPlayFrom?: (t: number) => void;
   onSeek?: (t: number, final: boolean) => void;
+  duration?: number;
 }) {
   const [clip, setClip] = useState(start);
   const [crop, setCrop] = useState<ClipCrop | null>(null);
@@ -67,7 +69,7 @@ function Harness({
         src={src}
         clip={clip}
         onChange={setClip}
-        duration={3600}
+        duration={duration}
         current={current}
         picture={16 / 9}
         crop={crop}
@@ -99,6 +101,53 @@ describe("ClipPanel", () => {
     expect(range()).toBe("140-170");
   });
 
+  it("keeps the focus in a time field that took a typed time on Enter", () => {
+    render(<Harness />);
+    const field = () => screen.getAllByRole("textbox", { name: "clip.in" })[0]!;
+    field().focus();
+    fireEvent.change(field(), { target: { value: "2:20" } });
+    fireEvent.keyDown(field(), { key: "Enter" });
+    expect(range()).toBe("140-170");
+    expect(document.activeElement).toBe(field());
+    expect((field() as HTMLInputElement).value).toBe("0:02:20.0");
+  });
+
+  it("shows the mark it holds, not a time it could not take", () => {
+    render(<Harness start={{ start: 3500, end: 3600 }} />);
+    const out = () => screen.getAllByRole("textbox", { name: "clip.out" })[0] as HTMLInputElement;
+    // Past the end: clamped back to the end, and the field says so.
+    fireEvent.change(out(), { target: { value: "1:15:00" } });
+    fireEvent.blur(out());
+    expect(range()).toBe("3500-3600");
+    expect(out().value).toBe("1:00:00.0");
+    expect(out().getAttribute("aria-invalid")).toBeNull();
+    // Not a time at all: kept for fixing, and marked as not taken.
+    fireEvent.change(out(), { target: { value: "abc" } });
+    fireEvent.blur(out());
+    expect(out().value).toBe("abc");
+    expect(out().getAttribute("aria-invalid")).toBe("true");
+    expect(range()).toBe("3500-3600");
+  });
+
+  it("takes a decimal comma, as a Hungarian hand types it", () => {
+    render(<Harness />);
+    const field = screen.getAllByRole("textbox", { name: "clip.in" })[0]!;
+    fireEvent.change(field, { target: { value: "1:42,5" } });
+    fireEvent.keyDown(field, { key: "Enter" });
+    expect(range()).toBe("102.5-130");
+  });
+
+  it("never seeks the player onto the item's very end (that would end it, and the clip with it)", () => {
+    const onSeek = vi.fn();
+    render(<Harness onSeek={onSeek} duration={600} start={{ start: 590, end: 595 }} />);
+    fireEvent.keyDown(screen.getByRole("slider", { name: "clip.out" }), { key: "End" });
+    expect(range()).toBe("590-600");
+    const [time, final] = onSeek.mock.lastCall!;
+    expect(final).toBe(true);
+    expect(time).toBeLessThan(600);
+    expect(time).toBeGreaterThan(599);
+  });
+
   it("marks an end at the playhead", () => {
     render(<Harness current={115.5} />);
     fireEvent.click(screen.getByRole("button", { name: "clip.outHere" }));