revert(android): roll back to build #6 (35642d1) — pre-oboe known-good state

Spent 10+ builds chasing a __init_tcb+4 / pthread_create SIGSEGV after
adding the oboe audio backend. Every "fix" made things worse. Reverting
all Android-specific files to the state at 35642d1 (build #6), which
was the last commit where the Tauri Android app actually launched,
rendered the home screen, and successfully registered on a relay.

Reverted files (all back to their 35642d1 content):
  - desktop/src-tauri/Cargo.toml        (no build-dep cc, no tracing-android)
  - desktop/src-tauri/build.rs          (git hash only, no Oboe / cc build)
  - desktop/src-tauri/src/lib.rs        (engine cfg-gated on non-android)
  - desktop/src-tauri/src/main.rs       (two-line desktop entry)
  - desktop/src-tauri/src/engine.rs     (desktop-only audio setup)
  - scripts/Dockerfile.android-builder  (no android24→26 clang shim)
  - scripts/build-tauri-android.sh      (no linker env vars / manifest patch)

Deleted (were added between b314138 and e2e023d):
  - desktop/src-tauri/cpp/getauxval_fix.c
  - desktop/src-tauri/cpp/oboe_bridge.{h,cpp}
  - desktop/src-tauri/cpp/oboe_stub.cpp
  - desktop/src-tauri/src/oboe_audio.rs

Next: rebuild image on remote (to drop the baked-in clang shim), build
an APK, install on Pixel 6, verify the UI renders the same way build #6
did. From there we add features back ONE at a time so we can actually
bisect which one triggers the tao::ndk_glue crash. User's rule:
"if you want to change stack, change incrementally, so we can debug".

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

desktop/src-tauri/Cargo.toml

@@ -17,10 +17,6 @@ path = "src/main.rs"
 
 [build-dependencies]
 tauri-build = { version = "2", features = [] }
-# cc is always available because build.rs runs on the HOST, not the TARGET.
-# We gate the actual cc::Build::new() calls on `target.contains("android")` at
-# build-script runtime.
-cc = "1"
 
 [dependencies]
 tauri = { version = "2", features = [] }
@@ -40,17 +36,11 @@ wzp-fec = { path = "../../crates/wzp-fec" }
 wzp-crypto = { path = "../../crates/wzp-crypto" }
 wzp-transport = { path = "../../crates/wzp-transport" }
 
-# wzp-client on desktop: full audio stack (CPAL + macOS VoiceProcessingIO)
+# wzp-client pulls CPAL + (on macOS) VoiceProcessingIO — desktop only.
+# Android gets an oboe/AAudio backend in Step 3 of the Tauri mobile rewrite.
 [target.'cfg(not(target_os = "android"))'.dependencies]
 wzp-client = { path = "../../crates/wzp-client", features = ["audio", "vpio"] }
 
-# wzp-client on Android: only the codec/handshake/call modules. Audio I/O is
-# handled by our own oboe_audio module (C++ Oboe bridge).
-[target.'cfg(target_os = "android")'.dependencies]
-wzp-client = { path = "../../crates/wzp-client", default-features = false }
-# On-device logcat bridge for the tracing crate — useful for native debugging.
-tracing-android = "0.2"
-
 # Platform-specific
 [target.'cfg(target_os = "macos")'.dependencies]
 coreaudio-rs = "0.11"