DeadAir in the page: a switch per show, one beside the speed, and the time saved (#172)

A DeadAir switch in each show's settings, and the same switch beside
the speed for the show that is playing, drawn as a waveform with its gap
closed up, outlined when off and solid when on, with aria-pressed. A
file the server gives a copy for plays from /media/{id}/deadair. An
episode's line says how much shorter it is, and Settings says how much
DeadAir has saved you.

Turning it on or off mid-episode saves the place with a request it waits
for, not a beacon, then asks for the entry again from the new
GET /api/entries/{feed}/{guid}, whose position is in the clock of the
version it now plays, and carries on there. A copy not made yet plays
from the next time. Turning a show on wakes the copy maker, so the copy
is there in seconds rather than at its next pass.

The browser test plays a real MP3 with long silences, quiet.mp3, from a
show it adds and removes itself.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/items.ts

@@ -78,6 +78,7 @@ function epEl(e){
         num&&`<span>${num}</span>`,
         left&&`<span>${left}</span>`,
         others>0&&`<span>+${others} more file${others===1?'':'s'}</span>`,
+        enc&&enc.deadair>0&&`<span title="DeadAir shortened its long silences">${shorter(enc.deadair)}</span>`,
         enc&&enc.last_error&&enc.state==='error'&&`<span style="color:var(--bad)">${esc(enc.last_error)}</span>`,
       ].filter(Boolean).join('<span class="dot"></span>')}</div>
     </div>