fix(clip): typed times belong to their value, and every mark on the player chrome can be seen

TimecodeField drops a draft when the value moves under it (another segment selected, a nudge), so
leaving the field never commits it to another cut; it is invalid only once offered, with a line
under it saying how to type a time. On the always-dark chrome media-scope points every focus ring
at --media-mark and errors at the new --media-danger (a light theme's accent and danger were under
3:1 there). A track whose dragged handle unmounts ends the drag on the pointer's release instead of
locking up; a remove refused while clips are queued leaves no focus to take later; each remove-cut
button names its cut and is a 24px target. DESIGN.md records the media tokens; stale comments fixed.

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

@@ -137,7 +137,7 @@ describe("ClipPanel", () => {
     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)", () => {
+  it("never seeks the player onto the item's very end (that would finish the item)", () => {
     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" });