step E(android): compile full Oboe C++ bridge (not yet called from Rust)

Fifth incremental variable — and the first genuinely heavy one. Adds:
  - cpp/oboe_bridge.{h,cpp} (copied verbatim from crates/wzp-android/cpp/)
  - cpp/oboe_stub.cpp (fallback if Oboe can't be fetched)
  - build.rs now clones google/oboe@1.8.1 into OUT_DIR and compiles
    oboe_bridge.cpp + every .cpp file under oboe/src/ as a single
    static library via cc::Build, using shared libc++. Same logic as
    the legacy wzp-android build.rs.
  - libc++_shared.so gets copied from the NDK sysroot into the Tauri
    gen/android jniLibs directory so the runtime linker can find it.
  - rustc-link-lib=log / OpenSLES emitted for Oboe's Android backends.

Deliberately NOT called from Rust yet — no extern "C" FFI declarations,
no oboe_audio.rs module, the `wzp_oboe_*` symbols from the static lib
are simply present but unreferenced.

Goal: isolate whether the Oboe C++ compile + static lib link alone
(with its libc++ dependency and log/OpenSLES bindings) regresses the
working baseline. If the build still launches and renders the home
screen, we know the C++ side is clean and the actual regression is
caused by calling into Oboe at runtime (next step).

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

desktop/src-tauri/cpp/oboe_bridge.h

@@ -0,0 +1,43 @@
+#ifndef WZP_OBOE_BRIDGE_H
+#define WZP_OBOE_BRIDGE_H
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+#include <atomic>
+typedef std::atomic<int32_t> wzp_atomic_int;
+extern "C" {
+#else
+#include <stdatomic.h>
+typedef atomic_int wzp_atomic_int;
+#endif
+
+typedef struct {
+    int32_t sample_rate;
+    int32_t frames_per_burst;
+    int32_t channel_count;
+} WzpOboeConfig;
+
+typedef struct {
+    int16_t* capture_buf;
+    int32_t  capture_capacity;
+    wzp_atomic_int* capture_write_idx;
+    wzp_atomic_int* capture_read_idx;
+
+    int16_t* playout_buf;
+    int32_t  playout_capacity;
+    wzp_atomic_int* playout_write_idx;
+    wzp_atomic_int* playout_read_idx;
+} WzpOboeRings;
+
+int wzp_oboe_start(const WzpOboeConfig* config, const WzpOboeRings* rings);
+void wzp_oboe_stop(void);
+float wzp_oboe_capture_latency_ms(void);
+float wzp_oboe_playout_latency_ms(void);
+int wzp_oboe_is_running(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // WZP_OBOE_BRIDGE_H