Add Wyoming protocol ASR server and nix devshell

New wyoming-whisper-rs binary crate implementing the Wyoming protocol
over TCP, making whisper-rs usable with Home Assistant's voice pipeline.
Includes nix flake devshell with Vulkan, ROCm/hipBLAS, clippy, and
rustfmt support.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+whisper-rs provides safe Rust bindings to [whisper.cpp](https://github.com/ggerganov/whisper.cpp), a C++ speech recognition library. It's a two-crate workspace:
+
+- **`whisper-rs`** (root) — Safe public API
+- **`whisper-rs-sys`** (`sys/`) — FFI bindings generated via bindgen, with a CMake-based build of the whisper.cpp submodule
+
+The upstream C++ source lives in `sys/whisper.cpp/` (git submodule — clone with `--recursive`).
+
+## Build Commands
+
+```bash
+cargo build                                    # Default build
+cargo build --release --features vulkan        # With Vulkan GPU support
+cargo build --release --features hipblas       # With AMD ROCm support
+cargo build --release --features cuda          # With NVIDIA CUDA support
+cargo test                                     # Run all tests
+cargo fmt                                      # Format code
+cargo clippy                                   # Lint
+```
+
+**Running examples** (require a GGML model file and a WAV audio file):
+```bash
+cargo run --example basic_use -- model.bin audio.wav
+cargo run --example audio_transcription -- model.bin audio.wav
+cargo run --example vad -- model.bin audio.wav output.wav
+```
+
+**Skipping bindgen** (use pre-generated bindings): set `WHISPER_DONT_GENERATE_BINDINGS=1`.
+
+All `WHISPER_*` and `CMAKE_*` env vars are forwarded to the CMake build.
+
+## Architecture
+
+```
+whisper-rs (safe Rust API)
+  → whisper-rs-sys (bindgen FFI)
+    → whisper.cpp (C++ submodule, built via CMake)
+      → GGML (tensor library with CPU/GPU backends)
+```
+
+**Key types and their relationships:**
+
+- `WhisperContext` — Arc-wrapped model handle, thread-safe, created from a model file
+- `WhisperState` — Inference state created from a context; multiple states can share one context
+- `FullParams` — Transcription configuration (sampling strategy, language, callbacks)
+- `WhisperSegment` / `WhisperToken` — Result types with timestamps and probabilities
+
+**Core flow:** `WhisperContext::new_with_params()` → `ctx.create_state()` → `state.full(params, &audio_data)` → iterate segments via `state.as_iter()`
+
+**Module layout in `src/`:**
+- `whisper_ctx.rs` — Raw context wrapper (`WhisperInnerContext`)
+- `whisper_ctx_wrapper.rs` — Safe public `WhisperContext`
+- `whisper_state/` — State management, segments, tokens, iterators
+- `whisper_params.rs` — `FullParams`, `SamplingStrategy` (Greedy / BeamSearch)
+- `whisper_vad.rs` — Voice Activity Detection
+- `whisper_grammar.rs` — GBNF grammar-constrained decoding
+- `vulkan.rs` — Vulkan device enumeration (behind `vulkan` feature)
+
+## Build System (sys/build.rs)
+
+The build script:
+1. Copies `whisper.cpp` sources into `OUT_DIR`
+2. Runs bindgen on `wrapper.h` to generate FFI bindings (falls back to `src/bindings.rs` on failure)
+3. Configures and builds whisper.cpp via CMake with feature-dependent flags (`GGML_CUDA`, `GGML_HIP`, `GGML_VULKAN`, `GGML_METAL`, etc.)
+4. Statically links: `whisper`, `ggml`, `ggml-base`, `ggml-cpu`, plus backend-specific libs
+
+## Feature Flags
+
+| Feature | Purpose |
+|---------|---------|
+| `cuda` | NVIDIA GPU (needs CUDA toolkit) |
+| `hipblas` | AMD GPU via ROCm |
+| `metal` | Apple Metal GPU |
+| `vulkan` | Vulkan GPU |
+| `openblas` | OpenBLAS acceleration (requires `BLAS_INCLUDE_DIRS` env var) |
+| `openmp` | OpenMP threading |
+| `coreml` | Apple CoreML |
+| `intel-sycl` | Intel SYCL |
+| `raw-api` | Re-export `whisper-rs-sys` types publicly |
+| `log_backend` | Route C++ logs to the `log` crate |
+| `tracing_backend` | Route C++ logs to the `tracing` crate |
+
+## Nix Development Environment
+
+The `flake.nix` provides a devshell with all dependencies for Vulkan and ROCm/hipBLAS builds. Use `direnv allow` or `nix develop` to enter the environment. Key env vars (`LIBCLANG_PATH`, `BINDGEN_EXTRA_CLANG_ARGS`, `HIP_PATH`, `VULKAN_SDK`) are set automatically.
+
+## PR Conventions
+
+Per `.github/PULL_REQUEST_TEMPLATE.md`:
+- Run `cargo fmt` and `cargo clippy` before submitting
+- Self-review code for legibility
+- No GenAI-generated code in PRs