codecs: add native build scripts for libvpx/opus/speex + fix CMake includes

- scripts/build-native-codecs.sh: cross-compile libvpx, opus, speex for
  Android ABIs (arm64-v8a, armeabi-v7a, x86_64) using NDK clang with -fPIC
- scripts/android-ndk.sh: NDK root detection helper
- scripts/native-build-cache.sh: ccache detection helper
- scripts/init-third-party-submodules.sh: init codec submodules
- scripts/ensure-gradle-wrapper.sh: gradle wrapper sanity check
- scripts/adb-reconnect.sh: ADB device discovery helpers
- ndk/CMakeLists.txt: per-ABI include dirs for opus/ and speex_config_types.h

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/init-third-party-submodules.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+# Initialize only the codec-related git submodules needed for the NDK build.
+# Called by rebuild.sh before the native build step.
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+cd "$ROOT"
+
+SUBMODULES=(
+  "third-party/libvpx"
+  "third-party/opus"
+  "third-party/speex"
+  "third-party/wireguard-android"
+)
+
+for sm in "${SUBMODULES[@]}"; do
+  if [[ -d "$sm/.git" ]] || git -C "$sm" rev-parse --git-dir >/dev/null 2>&1; then
+    echo "==> Submodule already initialized: $sm"
+  else
+    echo "==> Initializing submodule: $sm"
+    git submodule update --init -- "$sm"
+  fi
+done