fix(player): clamp seeks inside media to stop end-of-stream pause loop (DR-095)

Seeking near the end of a transcoded video locked the player into a
stall/pause loop: unpausing or skipping bounced straight back to paused.

Both seek paths clamped the target to exactly `duration`. hls.js then
requested the segment whose start time lies *past* the end of the media
(a 6330.324s item asks for segment 1055, starting at 6336.33s). Jellyfin
never produces that segment, the fetch times out, and the gap-controller
stalls forever at the last buffered position — retrying ~1x/second and
firing an endless stream of AbortErrors as play() lands mid-nudge.

Clamp strictly inside the media instead, keeping one segment length
(6s) of margin, floored at 0 so short media still seeks to the start.
The seek-bar drag path needed this too: its range input `max` is the
duration itself, so dragging fully right produced the same dead target.

Also bumps the requirement-count fixture for the new DR-095 row.

scripts/extract-traces.test.ts

@@ -175,8 +175,8 @@ describe("live requirements.md", () => {
 
     expect(defined.UR).toBe(61);
     expect(defined.IR).toBe(29);
-    expect(defined.DR).toBe(91);
+    expect(defined.DR).toBe(92);
     expect(defined.JA).toBe(32);
-    expect(defined.total).toBe(213);
+    expect(defined.total).toBe(214);
   });
 });