feat: initiale Implementierung von corsairctl

Rust CLI-Tool für Corsair Bragi-Geräte (HS80 RGB Wireless, etc.).
Implementiert Protokoll-Kern, HID-Kommunikation, BragiDevice mit
RAII-Lifecycle, CLI-Subcommands (battery, sidetone, led, info, json,
udev), ALSA-Sidetone-Steuerung und Waybar-JSON-Output.

24 Unit-Tests für Packet-Bau, Response-Parsing und Property-Enums.

src/sidetone.rs

@@ -0,0 +1,64 @@
+// ABOUTME: ALSA-Mixer Integration für Sidetone-Steuerung.
+// ABOUTME: Liest und setzt den Sidetone-Wert über den ALSA-Mixer der Corsair-Soundkarte.
+
+use alsa::mixer::{Mixer, SelemChannelId, SelemId};
+
+use crate::error::Result;
+
+const CARD_NAME: &str = "Gaming";
+const SIDETONE_VOLUME: &str = "Sidetone Playback Volume";
+const SIDETONE_SWITCH: &str = "Sidetone Playback Switch";
+
+/// Findet die ALSA-Card-Nummer für die Corsair Gaming Soundkarte.
+fn find_card() -> Result<String> {
+    // ALSA-Cards durchiterieren
+    for card_idx in 0..32 {
+        let name = format!("hw:{card_idx}");
+        if let Ok(ctl) = alsa::Ctl::new(&name, false) {
+            if let Ok(info) = ctl.card_info() {
+                let card_name = info.get_name().unwrap_or_default();
+                if card_name.contains(CARD_NAME) {
+                    return Ok(name);
+                }
+            }
+        }
+    }
+    Err(crate::error::CorsairError::DeviceNotFound)
+}
+
+/// Liest den aktuellen Sidetone-Level (0-23).
+pub fn get_level() -> Result<i64> {
+    let card = find_card()?;
+    let mixer = Mixer::new(&card, false)?;
+
+    let selem_id = SelemId::new(SIDETONE_VOLUME, 0);
+    let selem = mixer
+        .find_selem(&selem_id)
+        .ok_or(crate::error::CorsairError::DeviceNotFound)?;
+
+    let value = selem.get_playback_volume(SelemChannelId::FrontLeft)?;
+    Ok(value)
+}
+
+/// Setzt den Sidetone-Level (0-23).
+pub fn set_level(level: i64) -> Result<()> {
+    let card = find_card()?;
+    let mixer = Mixer::new(&card, false)?;
+
+    // Volume setzen
+    let volume_id = SelemId::new(SIDETONE_VOLUME, 0);
+    let volume_elem = mixer
+        .find_selem(&volume_id)
+        .ok_or(crate::error::CorsairError::DeviceNotFound)?;
+
+    volume_elem.set_playback_volume_all(level)?;
+
+    // Switch aktivieren falls Level > 0
+    let switch_id = SelemId::new(SIDETONE_SWITCH, 0);
+    if let Some(switch_elem) = mixer.find_selem(&switch_id) {
+        let enabled = if level > 0 { 1 } else { 0 };
+        let _ = switch_elem.set_playback_switch_all(enabled);
+    }
+
+    Ok(())
+}