feat(host/windows): WASAPI loopback audio capture

Windows AudioCapturer via the wasapi crate (0.23): loopback the default render endpoint (Render device + Direction::Capture + shared mode => STREAMFLAGS_LOOPBACK) at 48 kHz stereo f32 with autoconvert, feeding the existing Opus path with no resampling. Dedicated COM-MTA thread owns the !Send WASAPI objects; interleaved f32 chunks leave over a bounded lossy channel; RAII Drop stops + joins. Bring-up handshake reports a missing endpoint as Err so a session continues without audio. open_audio_capture Windows factory arm + module. Init chain validated live on the VM (open succeeds; next_chunk waits on a silent system). Virtual mic deferred (no Windows virtual-audio endpoint). m3 audio_thread wiring + opus hoist land with the integration task.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Cargo.lock

@@ -2638,6 +2638,7 @@ dependencies = [
  "utoipa",
  "utoipa-axum",
  "utoipa-scalar",
+ "wasapi",
  "wayland-backend",
  "wayland-client",
  "wayland-protocols-misc",
@@ -3965,6 +3966,19 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "wasapi"
+version = "0.23.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "80c3aa5d6b0e7acc3ea10cb19c334df0c8d825060f14a30d9e3b03385e6e5175"
+dependencies = [
+ "log",
+ "num-integer",
+ "thiserror 2.0.18",
+ "windows",
+ "windows-core",
+]
+
 [[package]]
 name = "wasi"
 version = "0.11.1+wasi-snapshot-preview1"