feat(tui): say so in the status bar when the listener took another port

With the login screen's own attempts no longer holding the port, a
session listens somewhere other than the configured port mainly when
another program already holds it. soulseek-rs still falls back to an
ephemeral port there, which is what lets several clients on one machine
share a configured port, and it advertises the port it really bound. A
manual port forward on the router then points at nothing, though, and
the TUI never said so; the CLI already warns.

After login the TUI compares the bound port with the configured one,
using the CLI's rule, and the status bar's title reads "port X in use,
listening on Y" for the rest of the session. A window attached to a
daemon shows nothing: the daemon owns its listener.

Nicotine+ keeps retrying the configured port every five seconds and
Soulseek.NET refuses it; neither falls back. Keeping the fallback and
making it visible is a deliberate difference.

soulseek-rs/src/ui/main_tui/mod.rs

@@ -33,6 +33,7 @@ pub struct MainTui {
     saved_snapshot: Snapshot,
     /// Which divider the left mouse button is holding, if any.
     resize_drag: Option<input::ResizeDrag>,
+    listener_fallback: Option<(u16, u16)>,
 }
 
 impl MainTui {
@@ -53,6 +54,7 @@ impl MainTui {
             config_path,
             saved_snapshot: Snapshot::default(),
             resize_drag: None,
+            listener_fallback: None,
         };
         tui.restore_persisted_state();
         tui
@@ -257,9 +259,11 @@ pub fn launch_main_tui(
     search_timeout: Duration,
     store: Option<StateStore>,
     config_path: Option<std::path::PathBuf>,
+    listener_fallback: Option<(u16, u16)>,
 ) -> Result<TuiExit> {
-    let tui =
+    let mut tui =
         MainTui::new(client, download_dir, search_timeout, store, config_path);
+    tui.listener_fallback = listener_fallback;
     tui.run(terminal)
 }
 

soulseek-rs/src/ui/main_tui/render/mod.rs

@@ -40,6 +40,7 @@ impl MainTui {
             &self.state.downloads,
             self.state.active_downloads_count,
             daemon.as_deref(),
+            self.listener_fallback,
         );
 
         self.render_content(frame, main_chunks[1]);

soulseek-rs/src/ui/main_tui/tests/layout.rs

@@ -21,6 +21,19 @@ fn the_results_pane_has_the_whole_width_to_itself() {
     assert!(searches < downloads && downloads < info, "{row}");
 }
 
+#[test]
+fn a_listener_that_fell_back_says_so_in_the_status_bar() {
+    let mut tui = furnished_tui();
+    tui.listener_fallback = Some((2234, 50123));
+
+    let screen = screen_of(&mut tui);
+
+    assert!(
+        screen.contains("port 2234 in use, listening on 50123"),
+        "{screen}"
+    );
+}
+
 #[test]
 fn tab_and_shift_tab_walk_the_panes_in_legend_order() {
     let mut tui = furnished_tui();