Windows port Phase 2: cpal device enumeration

Give the Windows device pickers a real device list (Phase 0/1 left pw_cli
returning nothing off-Linux) and generalize enumeration into a
platform-neutral interface.

- audio/mod.rs: move AudioDevice here (neutral home), gate pw_cli to
  cfg(unix), and re-export enumerate_audio_devices per-platform (pw_cli on
  unix, cpal_impl on windows). Also drop a now-stale "no-op stub" doc note.
- cpal_impl.rs: add enumerate_audio_devices() — iterate the cpal host's
  input + output devices into AudioDevice (name == description == the cpal
  friendly name, which is what resolve() matches target_node against, so a
  saved selection round-trips), sorted by description.
- pw_cli.rs: use super::AudioDevice instead of a local copy; parsing +
  tests unchanged.
- app/mod.rs: one-line import change; the device-picker logic is untouched.

Verified: shipped Linux state green (build --locked, clippy, 316/316,
pw_cli parse tests 6/6); the cpal enumerator compiles against real cpal via
the Linux/ALSA toggle. Runtime device listing on Windows is pending a real
host (M2/M3). WASAPI names are less stable than PipeWire node names, so a
saved device may not always round-trip (falls back to default).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/mod.rs

@@ -2,7 +2,7 @@ use crate::core::{CoreController, messages::{CoreCommand, UiEvent}};
 use crate::network::PeerState;
 use crate::notify::{self, Sound};
 use crate::audio::eq::{EqSettings, EQ_GAIN_DB_MAX, EQ_GAIN_DB_MIN};
-use crate::audio::pw_cli::{AudioDevice, enumerate_audio_devices};
+use crate::audio::{AudioDevice, enumerate_audio_devices};
 use crate::config::{AppConfig, NetworkMode, RecordingMode, RoomLayout};
 use crate::hotkeys::{format_binding, HotkeyAction, HotkeyContext, KeyBinding};
 use crate::presence::PresenceMode;

src/audio/cpal_impl.rs

@@ -42,7 +42,7 @@ use ringbuf::{
     HeapRb,
 };
 
-use super::{AudioBackend, AudioError, PLAYBACK_CHANNELS, PLAYBACK_TARGET_SAMPLES};
+use super::{AudioBackend, AudioDevice, AudioError, PLAYBACK_CHANNELS, PLAYBACK_TARGET_SAMPLES};
 
 /// The one sample rate the pipeline supports (Opus + the 20 ms frame).
 const SAMPLE_RATE: u32 = 48_000;
@@ -143,6 +143,49 @@ impl AudioBackend for CpalBackend {
     }
 }
 
+// ---------------------------------------------------------------------------
+// Device enumeration (for the settings device pickers)
+// ---------------------------------------------------------------------------
+
+/// Enumerate WASAPI input/output devices via cpal, sorted by description to match
+/// the PipeWire backend's stable UI ordering.
+///
+/// cpal exposes a single friendly name per device, which is also what [`resolve`]
+/// matches `target_node` against — so `name` and `description` are the same string
+/// and a saved selection round-trips. Note: WASAPI device names are less stable
+/// across driver/endpoint changes than PipeWire node names, so a saved device may
+/// not always be found again; selection then falls back to the system default.
+pub fn enumerate_audio_devices() -> Vec<AudioDevice> {
+    let host = cpal::default_host();
+    let mut devices = Vec::new();
+
+    if let Ok(inputs) = host.input_devices() {
+        for device in inputs {
+            if let Ok(name) = device.name() {
+                devices.push(AudioDevice {
+                    description: name.clone(),
+                    name,
+                    is_input: true,
+                });
+            }
+        }
+    }
+    if let Ok(outputs) = host.output_devices() {
+        for device in outputs {
+            if let Ok(name) = device.name() {
+                devices.push(AudioDevice {
+                    description: name.clone(),
+                    name,
+                    is_input: false,
+                });
+            }
+        }
+    }
+
+    devices.sort_by(|a, b| a.description.cmp(&b.description));
+    devices
+}
+
 // ---------------------------------------------------------------------------
 // Device / config selection
 // ---------------------------------------------------------------------------

src/audio/mod.rs

@@ -66,9 +66,35 @@ pub mod pan;
 pub mod pipewire_impl;
 #[cfg(windows)]
 pub mod cpal_impl;
+#[cfg(unix)]
 pub mod pw_cli;
 pub mod recorder;
 
+/// A selectable audio device for the input/output pickers. `name` is the stable
+/// identifier the backend uses to request the device (`target_node`);
+/// `description` is the human-facing label shown in the UI. The two may be equal
+/// (cpal/WASAPI) or differ (PipeWire node name vs. description).
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct AudioDevice {
+    pub name: String,
+    pub description: String,
+    pub is_input: bool,
+}
+
+impl std::fmt::Display for AudioDevice {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.description)
+    }
+}
+
+// Enumerate audio input/output devices for the pickers (sorted by description),
+// returning the same `AudioDevice` shape regardless of platform: PipeWire
+// (`pw-cli`) on Linux, cpal/WASAPI on Windows.
+#[cfg(unix)]
+pub use pw_cli::enumerate_audio_devices;
+#[cfg(windows)]
+pub use cpal_impl::enumerate_audio_devices;
+
 /// The audio backend implementation for the current platform.
 ///
 /// The whole app constructs and threads this alias (via
@@ -77,8 +103,7 @@ pub mod recorder;
 /// [`AudioBackend`] trait, which is the only interface the core talks to.
 ///
 /// - Linux/Unix → PipeWire ([`pipewire_impl::PipeWireBackend`]).
-/// - Windows → cpal/WASAPI ([`cpal_impl::CpalBackend`]); a no-op stub until the
-///   Phase 1 capture/playback implementation lands.
+/// - Windows → cpal/WASAPI ([`cpal_impl::CpalBackend`]).
 #[cfg(unix)]
 pub type PlatformAudioBackend = pipewire_impl::PipeWireBackend;
 #[cfg(windows)]

src/audio/pw_cli.rs

@@ -1,18 +1,6 @@
+use super::AudioDevice;
 use std::process::Command;
 
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct AudioDevice {
-    pub name: String,
-    pub description: String,
-    pub is_input: bool,
-}
-
-impl std::fmt::Display for AudioDevice {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{}", self.description)
-    }
-}
-
 pub fn enumerate_audio_devices() -> Vec<AudioDevice> {
     let output = Command::new("pw-cli")
         .arg("list-objects")