The desktop runner needed a hand-generated fixture and the Android one needed
`-x :app:rustBuildUniversalDebug`, which nobody was going to remember. Both are
now `bun run test:player` and `bun run test:player:android`.
The fixture is generated on first use rather than committed: no media in the
repo, and an exact duration, which the seek assertions depend on.
The gradle exclusion carries its reason inline — raw gradle drives the Rust
build through Tauri's android-studio-script, which expects a dev-server address
file that only exists under `tauri android dev`, and the library already in
jniLibs is what the test process loads.
