fix(audio): a cancelled announcement really stops; oto's Close is a no-op

Clicking Cancel reached the daemon and the queue cancelled the item, but
the sound played on to the end: oto v3's Player.Close only relies on the
garbage collector's finalizer, so the player stayed in the mix. Pause takes
it out immediately; only the device buffer (about 100 ms) drains. Same fix
covers talk cancel and daemon shutdown.

Direct speech via spd-say: killing the waiting client did not stop
speech-dispatcher either; on cancel it now sends `spd-say -S`.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

internal/audio/oto.go

@@ -91,7 +91,12 @@ func (OtoSink) Play(ctx context.Context, data []byte) error {
 	player.Play()
 	for player.IsPlaying() {
 		if err := ctx.Err(); err != nil {
-			player.Close()
+			// Cancel: stop the sound NOW. oto's Close is a no-op that
+			// relies on the garbage collector's finalizer, so a cancelled
+			// announcement would play on to its end; Pause takes the
+			// player out of the mix immediately (only the device buffer,
+			// about 100 ms, drains).
+			player.Pause()
 			return err
 		}
 		if err := player.Err(); err != nil {