refactor(android): split session JNI into modules, HUD-gated stats, AAudio open retry

- native: the 756-line session.rs becomes session/{mod,connect,input,planes}.rs
  around a SessionHandle (connect lifecycle + trust, input plane shims, plane
  start/stop + stats drain).
- Decode-stats sampling is HUD-gated (nativeSetVideoStatsEnabled): with the
  overlay hidden the decode thread skips the per-AU clock read + lock; enabling
  resets the measurement window.
- audio: the AAudio open path is a per-sharing-mode try_open closure — the
  realtime callback state (ring, prime, free-list) is rebuilt per attempt, so a
  failed exclusive-mode try can't leak state into the shared-mode retry.
- Kotlin: ConnectScreen/StreamScreen slimmed by extracting ConnectDialogs,
  StatsOverlay and TouchInput.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

clients/android/native/src/session/input.rs

@@ -0,0 +1,159 @@
+//! Input plane: Kotlin capture → `NativeClient::send_input`.
+//!
+//! All shims 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
+//! compile everywhere (parity with nativeConnect/nativeClose). The wire codes are the GameStream
+//! conventions: buttons 1=left/2=middle/3=right/4=X1/5=X2; scroll axis 0=vertical/1=horizontal,
+//! signed 120-unit delta, +=up/right; keys are Windows VK (mapped from KEYCODE_* on the Kotlin side).
+
+use jni::objects::JObject;
+use jni::sys::{jboolean, jint, jlong};
+use jni::JNIEnv;
+use punktfunk_core::input::{InputEvent, InputKind};
+
+use super::SessionHandle;
+
+/// Shared shim body: guard against a `0` handle, deref, and push one [`InputEvent`].
+fn send_event(handle: jlong, kind: InputKind, code: u32, x: i32, y: i32, flags: u32) {
+    if handle == 0 {
+        return;
+    }
+    // SAFETY: live handle per the nativeConnect/nativeClose contract; send_input is &self.
+    let h = unsafe { &*(handle as *const SessionHandle) };
+    let _ = h.client.send_input(&InputEvent {
+        kind,
+        _pad: [0; 3],
+        code,
+        x,
+        y,
+        flags,
+    });
+}
+
+/// `NativeBridge.nativeSendPointerMove(handle, dx, dy)` — relative mouse motion (screen +y down).
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeSendPointerMove(
+    _env: JNIEnv,
+    _this: JObject,
+    handle: jlong,
+    dx: jint,
+    dy: jint,
+) {
+    send_event(handle, InputKind::MouseMove, 0, dx, dy, 0);
+}
+
+/// `NativeBridge.nativeSendPointerAbs(handle, x, y, surfaceWidth, surfaceHeight)` — absolute cursor
+/// position: the host moves the pointer to `x`/`y` in a `surfaceWidth`×`surfaceHeight` pixel space,
+/// normalizing against the size packed into `flags` as `(w << 16) | h` and mapping into the output
+/// region (it drops the event if that size is zero). This is the touch "direct pointing" path — the
+/// cursor jumps to the finger — and matches the Apple client's absolute touch forwarding.
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeSendPointerAbs(
+    _env: JNIEnv,
+    _this: JObject,
+    handle: jlong,
+    x: jint,
+    y: jint,
+    surface_width: jint,
+    surface_height: jint,
+) {
+    let w = (surface_width.max(0) as u32) & 0xffff;
+    let ht = (surface_height.max(0) as u32) & 0xffff;
+    send_event(handle, InputKind::MouseMoveAbs, 0, x, y, (w << 16) | ht);
+}
+
+/// `NativeBridge.nativeSendPointerButton(handle, button, down)` — one button transition.
+/// `button`: GameStream id (1=left, 2=middle, 3=right, 4=X1, 5=X2). `down`: 1=press, 0=release.
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeSendPointerButton(
+    _env: JNIEnv,
+    _this: JObject,
+    handle: jlong,
+    button: jint,
+    down: jboolean,
+) {
+    let kind = if down != 0 {
+        InputKind::MouseButtonDown
+    } else {
+        InputKind::MouseButtonUp
+    };
+    send_event(handle, kind, button as u32, 0, 0, 0);
+}
+
+/// `NativeBridge.nativeSendScroll(handle, axis, delta)` — one scroll step. `axis`: 0=vertical,
+/// 1=horizontal. `delta`: signed, WHEEL_DELTA(120)-scaled, +=up/right.
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeSendScroll(
+    _env: JNIEnv,
+    _this: JObject,
+    handle: jlong,
+    axis: jint,
+    delta: jint,
+) {
+    send_event(handle, InputKind::MouseScroll, axis as u32, delta, 0, 0);
+}
+
+/// `NativeBridge.nativeSendKey(handle, vk, down, mods)` — one key transition. `vk`: Windows
+/// Virtual-Key code (0 = unmapped → dropped). `down`: 1=press, 0=release. `mods`: VK modifier
+/// bitmask (0 for now — the host folds modifiers from the L/R modifier key events themselves).
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeSendKey(
+    _env: JNIEnv,
+    _this: JObject,
+    handle: jlong,
+    vk: jint,
+    down: jboolean,
+    mods: jint,
+) {
+    if vk == 0 {
+        return;
+    }
+    let kind = if down != 0 {
+        InputKind::KeyDown
+    } else {
+        InputKind::KeyUp
+    };
+    send_event(handle, kind, vk as u32, 0, 0, mods as u32);
+}
+
+// ---- Gamepad: Kotlin captures (KeyEvent/MotionEvent) → NativeClient::send_input ---------------
+// Single-pad model: exactly one controller, forwarded as pad 0 (flags = 0). Buttons carry the
+// gamepad::BTN_* bit in `code` and pressed/released in `x` (1/0); axes carry the gamepad::AXIS_* id
+// in `code` and the value in `x` (sticks i16 −32768..32767, +y = up; triggers 0..255). The host
+// accumulates the incremental events into its virtual xpad. Wire contract: input.rs::gamepad.
+
+/// `NativeBridge.nativeSendGamepadButton(handle, bit, down)` — one gamepad button transition.
+/// `bit`: a `gamepad::BTN_*` bit (e.g. BTN_A = 0x1000). `down`: 1=press, 0=release.
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeSendGamepadButton(
+    _env: JNIEnv,
+    _this: JObject,
+    handle: jlong,
+    bit: jint,
+    down: jboolean,
+) {
+    // flags = 0: pad index 0 — single-pad model.
+    send_event(
+        handle,
+        InputKind::GamepadButton,
+        bit as u32,
+        i32::from(down != 0),
+        0,
+        0,
+    );
+}
+
+/// `NativeBridge.nativeSendGamepadAxis(handle, axisId, value)` — one gamepad axis update.
+/// `axisId`: a `gamepad::AXIS_*` id (LS_X=0..RT=5). `value`: stick i16 (−32768..32767, +y=up) or
+/// trigger 0..255.
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeSendGamepadAxis(
+    _env: JNIEnv,
+    _this: JObject,
+    handle: jlong,
+    axis_id: jint,
+    value: jint,
+) {
+    // flags = 0: pad index 0 — single-pad model.
+    send_event(handle, InputKind::GamepadAxis, axis_id as u32, value, 0, 0);
+}