feat: promote linux native audio path

poc/linux_voice_test/VERIFICATION.md

@@ -0,0 +1,59 @@
+# linux_voice_test verification
+
+Date: 2026-05-25
+Host: Fedora-based Linux sandbox host
+
+## Commands
+
+```bash
+pkg-config --modversion libpipewire-0.3
+pkg-config --modversion libspa-0.2
+cd poc/linux_voice_test
+cargo check
+cargo run -- --list-devices
+```
+
+## Observed results
+
+`pkg-config` resolved the product Linux capture dependencies successfully:
+
+```text
+libpipewire-0.3 -> 1.6.5
+libspa-0.2 -> 0.2
+```
+
+Note: `pipewire-0.3` is not the correct pkg-config module name for the Rust
+PipeWire crates used here; the expected module is `libpipewire-0.3`.
+
+`cargo check` completed successfully after adding an empty `[workspace]` table
+to `poc/linux_voice_test/Cargo.toml` so the PoC can build independently from
+the root workspace.
+
+`cargo run -- --list-devices` completed successfully and printed:
+
+```text
+Backend: pipewire
+Input devices:
+  [0] Brio 500 Analog Stereo [43]
+  [1] Built-in Audio Analog Stereo [34]
+Backend: pipewire
+Output devices:
+  [0] Built-in Audio Digital Stereo (IEC958) [46]
+  [1] Navi 21/23 HDMI/DP Audio Controller Digital Stereo (HDMI 4) [50]
+```
+
+## What this does validate
+
+- PipeWire crate dependencies compile on this host
+- the host exposes the exact `libpipewire-0.3` and `libspa-0.2` pkg-config
+  modules used by the product Linux capture backend
+- PipeWire node enumeration works for both input and output
+- the PoC can target real device node ids reported by the running desktop audio
+  graph
+
+## What this does not validate
+
+- PulseAudio fallback runtime on this host
+- full microphone-to-speaker loopback quality over an extended session
+- Chanora product audio-engine integration
+- push-to-talk, VAD, Opus, jitter buffering, or per-user playback controls