fix(dl): take stalled from Transmission

A zero download rate is not a stalled torrent: one between peers reads
zero for a poll or two and finishes fine, and at §9.8's 15s cadence that
flicker would raise the one chip reserved for a download that never
finishes. Transmission already decides this with its own stalled window;
carry isStalled and use it.

crates/arr-api/src/downloads.rs

@@ -116,7 +116,10 @@ fn phase(torrent: &Torrent) -> DownloadPhase {
     } else {
         match torrent.state {
             TorrentState::Seeding => DownloadPhase::Seeding,
-            TorrentState::Downloading if torrent.download_rate == 0 => DownloadPhase::Stalled,
+            // Transmission's own verdict, not a zero rate: a torrent between
+            // peers reads zero for a poll or two and finishes fine, and
+            // §9.8's stalled chip is for the case that never does.
+            TorrentState::Downloading if torrent.is_stalled => DownloadPhase::Stalled,
             TorrentState::Downloading => DownloadPhase::Downloading,
             _ => DownloadPhase::Queued,
         }
@@ -148,6 +151,7 @@ mod tests {
                 download_rate: rate,
                 eta: None,
                 error: error.map(str::to_owned),
+                is_stalled: rate == 0,
                 download_dir: PathBuf::from("/downloads"),
                 labels: Vec::new(),
                 is_finished: false,

crates/arr-dl/src/lib.rs

@@ -75,6 +75,10 @@ pub struct Torrent {
     pub eta: Option<i64>,
     /// Transmission's error message, when the torrent has errored.
     pub error: Option<String>,
+    /// Transmission's own verdict that this torrent has gone quiet for longer
+    /// than its configured stalled window. A rate of zero is not the same
+    /// fact: a torrent between peers reads zero for one poll and is fine.
+    pub is_stalled: bool,
     pub download_dir: PathBuf,
     pub labels: Vec<String>,
     /// Transmission has stopped this torrent because its configured seeding
@@ -237,8 +241,8 @@ impl TransmissionClient {
                 json!({
                     "fields": [
                         "id", "name", "hashString", "status", "percentDone",
-                        "rateDownload", "eta", "errorString", "downloadDir",
+                        "rateDownload", "eta", "errorString", "isStalled",
-                        "labels", "isFinished"
+                        "downloadDir", "labels", "isFinished"
                     ]
                 }),
             )
@@ -398,6 +402,8 @@ struct RpcTorrent {
     eta: Option<i64>,
     #[serde(rename = "errorString", default)]
     error: String,
+    #[serde(rename = "isStalled", default)]
+    is_stalled: bool,
     #[serde(rename = "downloadDir")]
     download_dir: PathBuf,
     #[serde(default)]
@@ -428,6 +434,7 @@ impl From<RpcTorrent> for Torrent {
             download_rate: value.download_rate,
             eta: value.eta.filter(|eta| *eta >= 0),
             error: (!value.error.is_empty()).then_some(value.error),
+            is_stalled: value.is_stalled,
             download_dir: value.download_dir,
             labels: value.labels,
             is_finished: value.is_finished,