chore: update AGENTS.md with Linux backend build and voice assistant instructions

Author: cursoragent

AGENTS.md

@@ -11,8 +11,11 @@ This is a cross-platform SDK monorepo. On a Linux cloud VM, the buildable servic
 | Kotlin SDK (Android target) | `./gradlew :runanywhere-kotlin:compileDebugKotlinAndroid -Prunanywhere.testLocal=false` | Android unit tests require device/emulator | `./gradlew :runanywhere-kotlin:runKtlintCheckOverCommonMainSourceSet` | JVM target has a known issue: `RAGBridge.kt` in `jvmAndroidMain` imports `@Keep` from `androidx.annotation` which is unavailable for JVM compilation |
 | Web SDK (TypeScript) | `npm run build -w packages/core` (from `sdk/runanywhere-web/`) | N/A | `npm run typecheck -w packages/core` | `llamacpp` package has a pre-existing duplicate index signature TS error |
 | Web Example App | `npm run dev` (from `examples/web/RunAnywhereAI/`) | Manual browser testing at `localhost:5173` | N/A | Full Vite app, works in demo mode without WASM |
-| C++ Commons | `cmake -B build ... && cmake --build build` (from `sdk/runanywhere-commons/`) | Tests require model files | N/A | Must use `gcc`/`g++` on this VM (clang lacks C++ stdlib headers). Pass `-DRAC_BUILD_PLATFORM=OFF` on Linux |
+| C++ Commons (core) | `cmake -B build ... && cmake --build build` (from `sdk/runanywhere-commons/`) | `./build/tests/test_core --run-all` (13 tests, no models needed) | N/A | Must use `gcc`/`g++` via `CC=gcc CXX=g++` (clang lacks C++ stdlib headers). Pass `-DRAC_BUILD_PLATFORM=OFF` on Linux |
+| C++ Commons (full backends) | `CC=gcc CXX=g++ bash scripts/build-linux.sh --shared` | Backend tests need downloaded models | N/A | Builds onnx+llamacpp. RAG backend has pre-existing zero-size array bug; use `-DRAC_BACKEND_RAG=OFF`. Sherpa-ONNX v1.12.23 URL changed: use `sherpa-onnx-v{VER}-linux-x64-shared.tar.bz2` (no `-cpu` suffix) |
+| Linux Voice Assistant | `cmake -B build && cmake --build build` (from `Playground/linux-voice-assistant/`) | `./build/test-pipeline <audio.wav>` runs full VAD→STT→LLM→TTS pipeline | N/A | Requires: ALSA headers (`libasound2-dev`), built commons with backends, downloaded models (`./scripts/download-models.sh`). Audio capture needs real hardware; `test-pipeline` works headless |
 | iOS/Swift SDK | Not buildable | Not buildable | Not available | Requires macOS + Xcode |
+| Android emulator | Not runnable | Not runnable | N/A | No KVM support in cloud VM |
 
 ### Key Gotchas
 
@@ -23,6 +26,28 @@ This is a cross-platform SDK monorepo. On a Linux cloud VM, the buildable servic
 - **`local.properties`**: Auto-created at root, `sdk/runanywhere-kotlin/`, and `examples/android/RunAnywhereAI/` with `sdk.dir=/opt/android-sdk`.
 - **pre-commit hooks**: Installed via `pre-commit install`. Requires `git config --unset-all core.hooksPath` first if `core.hooksPath` is set.
 
+### Linux Voice Assistant Quick Start
+
+```bash
+# 1. Build commons with backends
+cd sdk/runanywhere-commons
+CC=gcc CXX=g++ cmake -B build-linux-x86_64 -DCMAKE_BUILD_TYPE=Release \
+  -DRAC_BUILD_BACKENDS=ON -DRAC_BACKEND_ONNX=ON -DRAC_BACKEND_LLAMACPP=ON \
+  -DRAC_BACKEND_RAG=OFF -DRAC_BUILD_SHARED=ON -DRAC_BUILD_PLATFORM=OFF
+cmake --build build-linux-x86_64 -j$(nproc)
+
+# 2. Copy libs to dist
+# (see build-linux.sh for full dist copy steps)
+
+# 3. Build voice assistant
+cd Playground/linux-voice-assistant
+CC=gcc CXX=g++ cmake -B build && cmake --build build
+
+# 4. Run test pipeline (headless, no mic needed)
+export LD_LIBRARY_PATH="../../sdk/runanywhere-commons/dist/linux/x86_64:../../sdk/runanywhere-commons/third_party/sherpa-onnx-linux/lib"
+./build/test-pipeline /path/to/audio.wav
+```
+
 ### Standard commands
 
 See `CLAUDE.md` for comprehensive build/test/lint commands for all SDK platforms. See `CONTRIBUTING.md` for contributor setup flow.