fix(cli): port live mode to ring API (read_frame/write_frame removed)

AudioCapture and AudioPlayback no longer expose the old read_frame()
and write_frame() methods — they were replaced with ring() returning
&Arc<AudioRing> when the lock-free SPSC ring was introduced. The CLI
live-mode loop still referenced the removed methods, which broke every
workspace build that touched wzp-client bin (including the remote
Linux x86_64 docker build).

- Send loop: allocate a 960-sample scratch buffer, fill it in a loop
  via capture.ring().read() until a full 20 ms frame is available,
  sleep 2 ms between empty reads to avoid hot-spinning.
- Recv loop: write decoded PCM into playback.ring() instead of
  calling write_frame(). Short writes on full ring drop the tail,
  which is the correct real-time behavior for CLI live mode.

No behavioral change on the wire or in the call pipeline — this is
purely a compile fix for cli.rs bitrot that accumulated since the
ring API landed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/wzp-client/src/cli.rs

@@ -626,11 +626,21 @@ async fn run_live(transport: Arc<wzp_transport::QuinnTransport>) -> anyhow::Resu
         .spawn(move || {
             let config = CallConfig::default();
             let mut encoder = CallEncoder::new(&config);
+            let mut frame = vec![0i16; FRAME_SAMPLES];
             loop {
-                let frame = match capture.read_frame() {
-                    Some(f) => f,
-                    None => break,
-                };
+                // Pull a full 20 ms frame from the capture ring. The ring
+                // may return a partial read when the CPAL callback hasn't
+                // produced enough samples yet — keep reading until we
+                // accumulate a whole frame, sleeping briefly on empty
+                // returns so we don't hot-spin the CPU.
+                let mut filled = 0usize;
+                while filled < FRAME_SAMPLES {
+                    let n = capture.ring().read(&mut frame[filled..]);
+                    filled += n;
+                    if n == 0 {
+                        std::thread::sleep(std::time::Duration::from_millis(2));
+                    }
+                }
                 let packets = match encoder.encode_frame(&frame) {
                     Ok(p) => p,
                     Err(e) => {
@@ -661,7 +671,13 @@ async fn run_live(transport: Arc<wzp_transport::QuinnTransport>) -> anyhow::Resu
                     // Repair packets feed the FEC decoder but don't produce audio.
                     if !is_repair {
                         if let Some(_n) = decoder.decode_next(&mut pcm_buf) {
-                            playback.write_frame(&pcm_buf);
+                            // Push the decoded frame into the playback
+                            // ring. The CPAL output callback drains from
+                            // here on its own clock; if the ring is full
+                            // (rare in CLI live mode) the write returns
+                            // a short count and the tail is dropped,
+                            // which is the correct real-time behavior.
+                            playback.ring().write(&pcm_buf);
                         }
                     }
                 }