feat(audio,android): add MobileVoiceAudioBackend + AndroidVoiceUnit (oboe-rs)

Add the cross-platform MobileVoiceAudioBackend trait, plus the
Android implementation AndroidVoiceUnit backed by oboe-rs 0.6.x.
AndroidVoiceUnit owns AAudio stream setup with VoiceCommunication
usage/preset, performance-mode LowLatency request, sharing-mode
Exclusive best-effort, hardware AEC/NS/AGC engagement via JNI, and
the diagnostics snapshot publish path used by SDD-116 evidence
collection.

Cargo.toml: adds oboe = "0.6" under the Android target.

Trace: SDD-111, SDD-112, SDD-113, SRS-210, SRS-211, SRS-212, SRS-213,
SRS-214.

crates/chanora_audio/Cargo.toml

@@ -61,6 +61,12 @@ reqwest = { version = "0.13", default-features = false, features = ["charset", "
 # by the bridge crate's android_init shim.
 jni = { version = "0.21", default-features = false }
 ndk-context = "0.1"
+# Oboe-rs (Google Oboe wrapper) for low-latency voice capture + playback.
+# Primary backend for SDD-111..SDD-115. The pre-compiled static library
+# shipped with `oboe-sys` 0.6 covers armv7 / aarch64 / x86 / x86_64.
+# Default features keep the precompiled library + pregenerated bindings
+# so we avoid the clang-sys / libclang requirement on the build host.
+oboe = "0.6"
 
 [target.'cfg(target_os = "windows")'.dependencies]
 # Real Windows global PTT (SDD-083 / SDD-084): RegisterRawInputDevices