feat: add Bytebeat Speed and Glide options to Bytebeat submenu (#36)

* feat: add Bytebeat Speed and Glide menu options with auto-wander engine

- Engine: add drone_countdown per BytebeatOscillator, drone_glide_enabled
  and drone_speed (1-8) to BytebeatState; add set_bytebeat_drone_speed /
  set_bytebeat_drone_glide methods; auto-wander logic in render loop picks
  scale-aware target Hz and glides over the full period using existing
  hz_ramp_rate machinery. Disabling snaps all oscillators back to
  base_frequency_hz immediately. 4 new engine tests.
- AudioCommand: add SetBytebeatDroneSpeed(u8) and SetBytebeatDroneGlide(bool)
  variants with dispatch in run_audio_loop.
- Menu: add bb_speed (u8, 1-8) and bb_glide (bool) fields to MenuState;
  expand Bytebeat submenu from 5 to 7 items (Speed: Nx, Glide: On/Off);
  update increment/decrement/lines; fix item-count test; add 5 new menu tests.
- App: track old_bb_speed / old_bb_glide and dispatch both AudioCommands on
  change.

Agent-Logs-Url: https://github.com/danvincent/pirate-synth/sessions/e19adde1-0bde-431d-b4dd-235a5f277bb6

Co-authored-by: danvincent <2820964+danvincent@users.noreply.github.com>

* feat: add Glacial Bytebeat S&H FM mode

Agent-Logs-Url: https://github.com/danvincent/pirate-synth/sessions/b40701ba-eb12-42ec-b42c-c0966708e4f7

Co-authored-by: danvincent <2820964+danvincent@users.noreply.github.com>

* refactor: extract BB_GLACIAL_T_PERIOD_SECS constant and clarify bb_speed comment

Agent-Logs-Url: https://github.com/danvincent/pirate-synth/sessions/b40701ba-eb12-42ec-b42c-c0966708e4f7

Co-authored-by: danvincent <2820964+danvincent@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: danvincent <2820964+danvincent@users.noreply.github.com>

Author: Copilot

crates/app/src/main.rs

@@ -1275,6 +1275,9 @@ fn main() -> Result<()> {
             let old_bb_active = menu.bb_active;
             let old_bb_volume = menu.bb_volume;
             let old_bb_osc_count = menu.bb_osc_count;
+            let old_bb_speed = menu.bb_speed;
+            let old_bb_glide = menu.bb_glide;
+            let old_bb_glacial_fm = menu.bb_glacial_fm;
 
             menu.apply_button(button);
             display.draw_menu(&menu)?;
@@ -1390,6 +1393,27 @@ fn main() -> Result<()> {
                     warn!("failed to send bytebeat oscillator count: {err}");
                 }
             }
+            if menu.bb_speed != old_bb_speed {
+                if let Err(err) =
+                    audio_tx.try_send(AudioCommand::SetBytebeatDroneSpeed(menu.bb_speed))
+                {
+                    warn!("failed to send bytebeat drone speed: {err}");
+                }
+            }
+            if menu.bb_glide != old_bb_glide {
+                if let Err(err) =
+                    audio_tx.try_send(AudioCommand::SetBytebeatDroneGlide(menu.bb_glide))
+                {
+                    warn!("failed to send bytebeat drone glide: {err}");
+                }
+            }
+            if menu.bb_glacial_fm != old_bb_glacial_fm {
+                if let Err(err) =
+                    audio_tx.try_send(AudioCommand::SetBytebeatGlacialFm(menu.bb_glacial_fm))
+                {
+                    warn!("failed to send bytebeat glacial FM: {err}");
+                }
+            }
         }
 
         synth.poll();

crates/audio_alsa/src/lib.rs

@@ -65,6 +65,9 @@ pub enum AudioCommand {
     SetBytebeatActive(bool),
     SetBytebeatOscillatorCount(usize),
     SetBytebeatRandomAlgo { enabled: bool, period_samples: u64 },
+    SetBytebeatDroneSpeed(u8),
+    SetBytebeatDroneGlide(bool),
+    SetBytebeatGlacialFm(bool),
     Stop,
 }
 
@@ -141,6 +144,9 @@ fn run_audio_loop(
                 AudioCommand::SetBytebeatRandomAlgo { enabled, period_samples } => {
                     engine.set_bytebeat_random_algo(enabled, period_samples)
                 }
+                AudioCommand::SetBytebeatDroneSpeed(speed) => engine.set_bytebeat_drone_speed(speed),
+                AudioCommand::SetBytebeatDroneGlide(enabled) => engine.set_bytebeat_drone_glide(enabled),
+                AudioCommand::SetBytebeatGlacialFm(enabled) => engine.set_bytebeat_glacial_fm(enabled),
                 AudioCommand::Stop => {
                     drop(stdin);
                     let _ = child.wait();