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/lib/timecode.test.ts

@@ -29,8 +29,13 @@ describe("parseTimecode", () => {
     expect(parseTimecode(" 90.5 ")).toBeCloseTo(90.5);
   });
 
+  it("takes a decimal comma, in the seconds only", () => {
+    expect(parseTimecode("1:02,5")).toBeCloseTo(62.5);
+    expect(parseTimecode("12,4")).toBeCloseTo(12.4);
+  });
+
   it("is null for what is not a timecode", () => {
-    for (const v of ["", "abc", "1::2", "1:2:3:4", "-5", "1:-2"])
+    for (const v of ["", "abc", "1::2", "1:2:3:4", "-5", "1:-2", "1,5:00", "1:02,5,5"])
       expect(parseTimecode(v)).toBeNull();
   });
 });