Show that DeadAir is still working on an episode (#176)

A new download in a show with DeadAir on plays at full length until its
copy is made, and nothing said so. Each file now carries
deadair_pending while DeadAir is on for its show and the copy is still
to come (not for one heard through, which it passes over), and the
episode's line and details say "Cutting dead air…". The maker sends a
deadair_done event when it finishes a file, and the page takes the list
again, so the line becomes how much shorter the episode is without a
reload.

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

src/ipc.rs

@@ -32,6 +32,8 @@ pub enum Event {
     DownloadDone { feed: String, enclosure: i64, url: String, path: String, bytes: u64 },
     DownloadError { feed: String, enclosure: i64, url: String, msg: String },
     TorrentDeferred { feed: String, url: String },
+    /// DeadAir finished a file's copy (#171), so a page showing it as in progress can stop.
+    DeadairDone { feed: String, enclosure: i64, saved_s: i64 },
     Reaped { path: String, bytes: u64 },
     /// Terminal: a client that asked for work stops reading here.
     ScanDone { feeds: usize },
@@ -79,6 +81,7 @@ impl Event {
             // Noise in a terminal; a UI still gets them on the socket.
             Event::FeedStart { feed } => format!("{feed}: checking"),
             Event::TorrentDeferred { feed, .. } => format!("{feed}: torrent deferred"),
+            Event::DeadairDone { feed, saved_s, .. } => format!("{feed}: DeadAir copy made, {saved_s} s shorter"),
             Event::ScanDone { feeds } => format!("scan complete, {feeds} feed(s)"),
         })
     }