perf: cache and sort microphone inputs once instead of every frame (#27)

In `draw_footer`, the `all_inputs` HashMap was being collected into a Vec
and sorted on every single UI frame (~60 FPS). This caused unnecessary
overhead and allocations.

This commit introduces a cached `all_inputs_sorted` vector in the
`AudioPlayerState` which is populated only when the inputs map changes
during the state sync. `draw_footer` now loops over this pre-sorted
vector directly.

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

src/gui/draw.rs

@@ -498,9 +498,7 @@ impl SoundpadGui {
         ui.add_space(5.0);
         ui.horizontal(|ui| {
             // ---------- Microphone selection ----------
-            let mut mics: Vec<(&String, &String)> =
-                self.audio_player_state.all_inputs.iter().collect();
-            mics.sort_by_key(|(k, _)| *k);
+            let mics = &self.audio_player_state.all_inputs_sorted;
 
             let mut selected_input = self.audio_player_state.current_input.to_owned();
             let prev_input = selected_input.to_owned();
@@ -514,7 +512,7 @@ impl SoundpadGui {
                 )
                 .show_ui(ui, |ui| {
                     for (name, nick) in mics {
-                        ui.selectable_value(&mut selected_input, name.to_owned(), nick);
+                        ui.selectable_value(&mut selected_input, name.clone(), nick);
                     }
                 });
 

src/types/gui.rs

@@ -55,6 +55,7 @@ pub struct AudioPlayerState {
 
     pub current_input: String,
     pub all_inputs: HashMap<String, String>,
+    pub all_inputs_sorted: Vec<(String, String)>,
 
     pub is_daemon_running: bool,
 }

src/utils/gui.rs

@@ -90,7 +90,18 @@ pub fn start_app_state_thread(audio_player_state_shared: Arc<Mutex<AudioPlayerSt
                     .next()
                     .unwrap_or_default()
                     .to_string();
-                guard.all_inputs = full_state.all_inputs;
+
+                if guard.all_inputs != full_state.all_inputs {
+                    guard.all_inputs = full_state.all_inputs;
+                    let mut sorted: Vec<(String, String)> = guard
+                        .all_inputs
+                        .iter()
+                        .map(|(k, v)| (k.clone(), v.clone()))
+                        .collect();
+                    sorted.sort_by(|a, b| a.0.cmp(&b.0));
+                    guard.all_inputs_sorted = sorted;
+                }
+
                 guard.is_daemon_running = true;
             }