feat(core+host+android): committed-text input plane (IME path) — InputKind::TextInput

The VK key-event vocabulary cannot express text an input method COMMITS
(autocorrect, gesture typing, non-Latin scripts, emoji). Add a first-class
text event and negotiate it:

- punktfunk-core: InputKind::TextInput (= 15) carries one Unicode scalar per
  event in `code`; HOST_CAP_TEXT_INPUT (0x04) in Welcome::host_caps.
- Host advertises the cap only where the session's inject backend can type
  text: Windows SendInput (KEYEVENTF_UNICODE, surrogate-pair aware) and the
  Linux wlroots backend — a dedicated second zwp_virtual_keyboard whose xkb
  keymap grows Unicode keysyms on demand (the wtype model), so keymap
  re-uploads never disturb the main device's layout/modifier state. The
  KWin-fake-input/libei/gamescope backends can only press layout keycodes, so
  those sessions don't set the bit and clients keep the VK fallback.
- GameStream plane: Moonlight's UTF-8 text packet (MAGIC_UTF8, previously
  recognized-and-dropped) now decodes to the same TextInput events.
- Android: KeyCaptureView picks a real editable InputConnection when the host
  has the cap — the IME runs its full machinery, mirrored to the host live via
  common-prefix diffs of the composition (backspaces + new suffix), with
  setComposingRegion adopting committed text so autocorrect-revert flows diff
  instead of retyping; newline→Enter, deleteSurroundingText→Backspace/Delete.
  Older hosts keep the TYPE_NULL raw-key path unchanged.
- keymap: media VKs (0xB0-0xB3) → evdev so the Android media keys land on
  Linux hosts too.

Verified: punktfunk-core + host gamestream + pf-inject tests green on Linux
(Ubuntu box), clippy clean; Android app+native builds.

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

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

@@ -6,11 +6,11 @@
 //! 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::{JByteBuffer, JObject};
+use jni::objects::{JByteBuffer, JObject, JString};
 use jni::sys::{jboolean, jint, jlong};
 use jni::JNIEnv;
 use punktfunk_core::input::{InputEvent, InputKind};
-use punktfunk_core::quic::{RichInput, HID_REPORT_MAX};
+use punktfunk_core::quic::{RichInput, HID_REPORT_MAX, HOST_CAP_TEXT_INPUT};
 
 use super::SessionHandle;
 
@@ -145,6 +145,45 @@ pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeSendKey(
     send_event(handle, kind, vk as u32, 0, 0, mods as u32);
 }
 
+/// `NativeBridge.nativeTextInputSupported(handle)` — whether the host advertised
+/// `HOST_CAP_TEXT_INPUT` (its inject backend types committed text), so the Kotlin side can pick
+/// the real IME `InputConnection` over the TYPE_NULL raw-key fallback. `0` handle → false.
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeTextInputSupported(
+    _env: JNIEnv,
+    _this: JObject,
+    handle: jlong,
+) -> jboolean {
+    if handle == 0 {
+        return 0;
+    }
+    // SAFETY: live handle per the nativeConnect/nativeClose contract; host_caps is &self.
+    let h = unsafe { &*(handle as *const SessionHandle) };
+    u8::from(h.client.host_caps() & HOST_CAP_TEXT_INPUT != 0)
+}
+
+/// `NativeBridge.nativeSendText(handle, text)` — committed IME text, one `TextInput` event per
+/// Unicode scalar (`code` = the scalar; multi-char commits are consecutive events in order).
+/// Control characters are skipped — Enter/Backspace/Tab ride the VK key path. Call only when
+/// [`Java_io_unom_punktfunk_kit_NativeBridge_nativeTextInputSupported`] returned true.
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeSendText(
+    mut env: JNIEnv,
+    _this: JObject,
+    handle: jlong,
+    text: JString,
+) {
+    if handle == 0 {
+        return;
+    }
+    let Ok(s) = env.get_string(&text) else {
+        return;
+    };
+    for ch in String::from(s).chars().filter(|c| !c.is_control()) {
+        send_event(handle, InputKind::TextInput, ch as u32, 0, 0, 0);
+    }
+}
+
 // ---- Gamepad: Kotlin captures (KeyEvent/MotionEvent) → NativeClient::send_input ---------------
 // Multi-pad model: each physical controller is forwarded on its own wire pad index (0..15), carried
 // in the low byte of `flags` on every per-pad event — the Kotlin side (`GamepadRouter`) assigns a