feat(android): mic uplink + connect-screen redesign

Microphone uplink (client → host's virtual mic, 0xCB) and a cleaner connect screen.

Mic (Rust-heavy, mirrors the audio playback path in reverse):
- crates/punktfunk-android/src/mic.rs: AAudio LowLatency **input** → realtime callback hands
  captured f32 to a channel → a worker thread Opus-encodes 20 ms stereo frames (48 kHz, VOIP,
  64 kbps) and calls NativeClient::send_mic. MicCapture owns the stream + encode thread (RAII stop).
- session.rs: SessionHandle gains a `mic` slot; nativeStartMic/nativeStopMic JNI (mirror of audio);
  stopped in Drop. NativeBridge: the two externs.
- Settings: a `micEnabled` flag + a Microphone toggle in SettingsScreen that requests RECORD_AUDIO
  (denied → stays off). StreamScreen starts the mic only if enabled AND the permission is held.

Connect-screen redesign:
- One scrollable Column (was a fixed centered layout that could clip with the new tab bar);
  host rows render via forEach (no nested LazyColumn). Colored section labels ("Saved hosts",
  "Discovered on the network", "Connect manually"), full-width host cards / fields / Connect button,
  a header + subtitle, and a muted footer.

Verified live (emulator pf_phone -> home-worker-2): toggling mic requests RECORD_AUDIO; with it
granted, a session sends mic frames (client "mic: sent=250 … peak=0.439" — real audio) and the host
logs "client datagram stream ended … mic=276". Redesigned screen confirmed via screenshots.

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

crates/punktfunk-android/src/lib.rs

@@ -26,6 +26,8 @@ mod audio;
 #[cfg(target_os = "android")]
 mod decode;
 mod feedback;
+#[cfg(target_os = "android")]
+mod mic;
 mod session;
 
 /// Initialize `android_logger` once when the JVM loads the library. Logs land in logcat under the

crates/punktfunk-android/src/mic.rs

@@ -0,0 +1,174 @@
+//! Android microphone uplink (android-only): capture mic PCM via AAudio (LowLatency **input**),
+//! Opus-encode 20 ms stereo frames, and push them to the host over the connector's mic plane
+//! (`send_mic` → 0xCB datagram). The mirror of [`crate::audio`] in reverse: AAudio's realtime input
+//! callback hands captured interleaved f32 to a channel; a worker thread we own does the Opus encode
+//! + send (encoding is too heavy for the realtime callback, exactly as decode is on the playback
+//! side). Format matches the host decoder + the Linux client: 48 kHz **stereo**, 20 ms, Opus VOIP.
+
+use ndk::audio::{
+    AudioCallbackResult, AudioDirection, AudioFormat, AudioPerformanceMode, AudioSharingMode,
+    AudioStream, AudioStreamBuilder,
+};
+use punktfunk_core::client::NativeClient;
+use std::collections::VecDeque;
+use std::ffi::c_void;
+use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
+use std::sync::mpsc::{sync_channel, Receiver, RecvTimeoutError, TrySendError};
+use std::sync::Arc;
+use std::time::{Duration, SystemTime, UNIX_EPOCH};
+
+const CHANNELS: usize = 2;
+const SAMPLE_RATE: i32 = 48_000;
+/// 20 ms per channel @ 48 kHz — the Linux client's frame; the host accepts ≤ 120 ms.
+const FRAME_SAMPLES: usize = 960;
+/// Captured-chunk hand-off depth (each ~ one burst); drops on overflow (best-effort uplink).
+const RING_CHUNKS: usize = 64;
+/// Opus VOIP target bitrate (speech; tunable).
+const MIC_BITRATE: i32 = 64_000;
+
+/// Owned by [`crate::session::SessionHandle`]: the live AAudio input stream + the encode thread.
+pub struct MicCapture {
+    _stream: AudioStream, // dropping it stops + closes the AAudio input stream
+    shutdown: Arc<AtomicBool>,
+    join: Option<std::thread::JoinHandle<()>>,
+}
+
+impl MicCapture {
+    /// Open AAudio (LowLatency, 48 kHz/stereo/f32) for **input** with a realtime callback that
+    /// forwards captured PCM to a channel, then spawn the Opus encode + uplink thread. `None` on
+    /// failure (the caller leaves the rest of the session streaming).
+    pub fn start(client: Arc<NativeClient>) -> Option<MicCapture> {
+        let (tx, rx) = sync_channel::<Vec<f32>>(RING_CHUNKS);
+        let captured = Arc::new(AtomicU64::new(0));
+        let cb_captured = captured.clone();
+
+        let callback = move |_s: &AudioStream, data: *mut c_void, num_frames: i32| {
+            let n = num_frames as usize * CHANNELS;
+            // SAFETY: for an input stream AAudio provides `num_frames * channel_count` captured F32
+            // samples at `data` (read-only for us).
+            let inp = unsafe { std::slice::from_raw_parts(data as *const f32, n) };
+            match tx.try_send(inp.to_vec()) {
+                Ok(()) | Err(TrySendError::Full(_)) => {} // drop-newest if the encoder lags
+                Err(TrySendError::Disconnected(_)) => return AudioCallbackResult::Stop,
+            }
+            cb_captured.fetch_add(num_frames as u64, Ordering::Relaxed);
+            AudioCallbackResult::Continue
+        };
+
+        let stream = AudioStreamBuilder::new()
+            .map_err(|e| log::error!("mic: AudioStreamBuilder::new: {e}"))
+            .ok()?
+            .direction(AudioDirection::Input)
+            .sample_rate(SAMPLE_RATE)
+            .channel_count(CHANNELS as i32)
+            .format(AudioFormat::PCM_Float)
+            .performance_mode(AudioPerformanceMode::LowLatency)
+            .sharing_mode(AudioSharingMode::Shared)
+            .data_callback(Box::new(callback))
+            .error_callback(Box::new(|_s, e| {
+                log::warn!("mic: AAudio error (device reroute/disconnect?): {e:?}");
+            }))
+            .open_stream()
+            .map_err(|e| log::error!("mic: open_stream (RECORD_AUDIO granted?): {e}"))
+            .ok()?;
+
+        if let Err(e) = stream.request_start() {
+            log::error!("mic: request_start: {e}");
+            return None;
+        }
+        log::info!(
+            "mic: AAudio input started rate={} ch={} fmt={:?}",
+            stream.sample_rate(),
+            stream.channel_count(),
+            stream.format(),
+        );
+
+        let shutdown = Arc::new(AtomicBool::new(false));
+        let sd = shutdown.clone();
+        let join = std::thread::Builder::new()
+            .name("pf-mic".into())
+            .spawn(move || encode_loop(client, rx, sd, captured))
+            .ok();
+
+        Some(MicCapture {
+            _stream: stream,
+            shutdown,
+            join,
+        })
+    }
+}
+
+impl Drop for MicCapture {
+    fn drop(&mut self) {
+        self.shutdown.store(true, Ordering::SeqCst);
+        if let Some(j) = self.join.take() {
+            let _ = j.join();
+        }
+        // `_stream` drops here → AAudio request_stop + close.
+    }
+}
+
+/// Consumer: drain captured f32 → accumulate → Opus `encode_float` 20 ms stereo frames → `send_mic`.
+fn encode_loop(
+    client: Arc<NativeClient>,
+    rx: Receiver<Vec<f32>>,
+    shutdown: Arc<AtomicBool>,
+    captured: Arc<AtomicU64>,
+) {
+    let mut enc = match opus::Encoder::new(
+        SAMPLE_RATE as u32,
+        opus::Channels::Stereo,
+        opus::Application::Voip,
+    ) {
+        Ok(e) => e,
+        Err(e) => {
+            log::error!("mic: opus encoder init: {e} — mic disabled");
+            return;
+        }
+    };
+    let _ = enc.set_bitrate(opus::Bitrate::Bits(MIC_BITRATE));
+
+    let frame = FRAME_SAMPLES * CHANNELS;
+    let mut ring: VecDeque<f32> = VecDeque::with_capacity(frame * 4);
+    let mut out = vec![0u8; 4000]; // max Opus packet for a 20 ms frame fits easily
+    let mut seq: u32 = 0;
+    let mut sent: u64 = 0;
+    let mut peak = 0f32; // loudest |sample| since the last log — tells speech from silence
+
+    while !shutdown.load(Ordering::Relaxed) {
+        match rx.recv_timeout(Duration::from_millis(100)) {
+            Ok(chunk) => ring.extend(chunk),
+            Err(RecvTimeoutError::Timeout) => continue, // wake to re-check shutdown
+            Err(RecvTimeoutError::Disconnected) => break,
+        }
+        while ring.len() >= frame {
+            let pcm: Vec<f32> = ring.drain(..frame).collect();
+            for &s in &pcm {
+                peak = peak.max(s.abs());
+            }
+            match enc.encode_float(&pcm, &mut out) {
+                Ok(len) => {
+                    let pts = SystemTime::now()
+                        .duration_since(UNIX_EPOCH)
+                        .map(|d| d.as_nanos() as u64)
+                        .unwrap_or(0);
+                    let _ = client.send_mic(seq, pts, out[..len].to_vec());
+                    seq = seq.wrapping_add(1);
+                    sent += 1;
+                    if sent % 250 == 0 {
+                        log::info!(
+                            "mic: sent={sent} captured_frames={} peak={peak:.3}",
+                            captured.load(Ordering::Relaxed),
+                        );
+                        peak = 0.0;
+                    }
+                }
+                Err(e) => log::debug!("mic: opus encode: {e}"),
+            }
+        }
+    }
+    log::info!(
+        "mic: stopped (sent={sent} captured_frames={})",
+        captured.load(Ordering::Relaxed),
+    );
+}

crates/punktfunk-android/src/session.rs

@@ -33,6 +33,8 @@ pub(crate) struct SessionHandle {
     video: Mutex<Option<VideoThread>>,
     #[cfg(target_os = "android")]
     audio: Mutex<Option<crate::audio::AudioPlayback>>,
+    #[cfg(target_os = "android")]
+    mic: Mutex<Option<crate::mic::MicCapture>>,
 }
 
 struct VideoThread {
@@ -57,6 +59,13 @@ impl SessionHandle {
     fn stop_audio(&self) {
         let _ = self.audio.lock().unwrap().take();
     }
+
+    /// Stop mic uplink. Dropping the [`crate::mic::MicCapture`] joins its encode thread and closes
+    /// the AAudio input stream. Idempotent.
+    #[cfg(target_os = "android")]
+    fn stop_mic(&self) {
+        let _ = self.mic.lock().unwrap().take();
+    }
 }
 
 impl Drop for SessionHandle {
@@ -64,6 +73,8 @@ impl Drop for SessionHandle {
         self.stop_video();
         #[cfg(target_os = "android")]
         self.stop_audio();
+        #[cfg(target_os = "android")]
+        self.stop_mic();
     }
 }
 
@@ -182,6 +193,8 @@ pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeConnect<'lo
                 video: Mutex::new(None),
                 #[cfg(target_os = "android")]
                 audio: Mutex::new(None),
+                #[cfg(target_os = "android")]
+                mic: Mutex::new(None),
             };
             Box::into_raw(Box::new(handle)) as jlong
         }
@@ -381,6 +394,47 @@ pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeStopAudio(
     }
 }
 
+/// `NativeBridge.nativeStartMic(handle)` — start mic capture (AAudio input → Opus → host `send_mic`).
+/// No-op if already running or on a `0` handle. Caller MUST hold RECORD_AUDIO; a failure (e.g. no
+/// permission) leaves the rest of the session streaming.
+#[cfg(target_os = "android")]
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeStartMic(
+    _env: JNIEnv,
+    _this: JObject,
+    handle: jlong,
+) {
+    if handle == 0 {
+        return;
+    }
+    // SAFETY: live handle per the nativeConnect/nativeClose contract.
+    let h = unsafe { &*(handle as *const SessionHandle) };
+    let mut guard = h.mic.lock().unwrap();
+    if guard.is_some() {
+        return; // already capturing
+    }
+    match crate::mic::MicCapture::start(h.client.clone()) {
+        Some(m) => *guard = Some(m),
+        None => log::error!("nativeStartMic: mic init failed (RECORD_AUDIO? — session unaffected)"),
+    }
+}
+
+/// `NativeBridge.nativeStopMic(handle)` — stop + join the mic thread and close the AAudio input
+/// stream (without closing the session). No-op on `0`.
+#[cfg(target_os = "android")]
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeStopMic(
+    _env: JNIEnv,
+    _this: JObject,
+    handle: jlong,
+) {
+    if handle != 0 {
+        // SAFETY: live handle per the contract.
+        let h = unsafe { &*(handle as *const SessionHandle) };
+        h.stop_mic();
+    }
+}
+
 // ---- Input plane: Kotlin capture → NativeClient::send_input ----------------------------------
 // All four are `&self` on the `Sync` connector (send_input is a non-blocking datagram push), safe
 // from the Kotlin UI thread. NOT android-gated — send_input exists on the host build too, so these