improved android client, feature parity with desktop

android/app/src/main/cpp/pstr_mpv.h

@@ -8,6 +8,9 @@ extern "C" {
 #endif
 int64_t pstr_android_stream_read(uint64_t handle, uint64_t offset, void *buffer, size_t length);
 int64_t pstr_android_stream_size(uint64_t handle);
+/// Interrupts an in-flight `pstr_android_stream_read`. A cancel with no reader
+/// waiting is dropped, so this is safe to call speculatively.
+void pstr_android_stream_cancel(uint64_t handle);
 void pstr_android_stream_release(uint64_t handle);
 #ifdef __cplusplus
 }