Third incremental variable. Previously the engine module was cfg-gated
out of the Android build entirely (`#[cfg(not(target_os = "android"))]
mod engine;` in lib.rs). Now it's always compiled, so any link-time
effect of having engine.rs in the compilation unit can be measured
against the working baseline from build #19.
Changes kept deliberately small:
- lib.rs: drop the cfg gate on `mod engine;`. `use engine::CallEngine`
stays gated because the Android-specific connect/disconnect/... stubs
in lib.rs don't reference the type.
- engine.rs: the `wzp_client::{audio_io, call}` imports + CodecId +
QualityProfile are gated to non-Android (they require the `audio`
feature on wzp-client which Android doesn't pull in). On Android we
keep only the MediaTransport import for transport.close(). The impl
block now has two `start()` methods: the full CPAL-backed one for
desktop, and a 6-line Android stub that returns `Err("audio engine
not yet wired on Android")` so attempts to `connect` from the UI
fail cleanly.
Goal: verify that linking in the compiled engine module (plus the
types it references) on Android doesn't regress the working baseline.
Home screen should still render and register_signal should still work.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
c69195fe06