android: the downloads say so in the shade

A Save still running with the app in the background now posts a progress
notice — how many files, the one it is on, a bar, Stop all and Open — and
takes it down when the queue empties. It sits on its own low-importance
channel so it can be silenced without silencing the player's card, and
rides its own dataSync foreground service rather than the media one: a
mediaPlayback service stops itself when the bar empties, a download is not
playback, and nothing else was keeping the process alive for a Save with
nothing playing — which is how the first real Save died, four tracks in.
Stop all goes through the same cancel(id) a row's tap takes, and Transfers
grew the matching button beside Clear finished. The walk pushes two rows
straight into the transfer store and reads the real notification back out
of `dumpsys notification`, without fetching anything.

Cargo.lock

@@ -197,6 +197,7 @@ dependencies = [
  "tauri-plugin-opener",
  "tauri-plugin-share",
  "tauri-plugin-storage",
+ "tauri-plugin-transfer-notice",
  "tauri-plugin-updater",
  "tempfile",
  "tokio",
@@ -5863,6 +5864,16 @@ dependencies = [
  "tauri-plugin",
 ]
 
+[[package]]
+name = "tauri-plugin-transfer-notice"
+version = "0.1.0"
+dependencies = [
+ "serde",
+ "serde_json",
+ "tauri",
+ "tauri-plugin",
+]
+
 [[package]]
 name = "tauri-plugin-updater"
 version = "2.11.0"