add AGENTS.md (#50)

Author: yoziru

AGENTS.md

@@ -0,0 +1,23 @@
+# AGENTS.md - TeslaBLE Development Guide
+
+## Build Commands
+```bash
+cmake -B build -DCMAKE_MESSAGE_LOG_LEVEL=ERROR && cmake --build build -j8 2>&1 | grep -E "error:|Error:|Built target|failed" | head -20 || true
+cd build && ctest -j1 --output-on-failure 2>&1 | grep -E "(FAILED.*\]|^[0-9]+% tests|expected equality|Which is:|tests/.*:.*:.*Failure|Failed to)"
+```
+
+## Architecture
+- **Library**: C++23 library for Tesla vehicle BLE communication
+- **Core Classes**: `Client` (main API), `CryptoContext` (keys/EC), `Peer` (sessions per domain)
+- **Domains**: VEHICLE_SECURITY, INFOTAINMENT (via `UniversalMessage_Domain`)
+- **Protocol**: Protobuf messages (nanopb), AES-GCM encryption (mbedtls)
+- **Dependencies**: nanopb, mbedtls, googletest
+- **Generated Code**: `generated/src/*.pb.c`, `generated/include/*.pb.h`
+
+## Code Style
+- **Namespace**: `TeslaBLE`
+- **Naming**: `PascalCase` classes, `snake_case` functions, `_` suffix for members (`crypto_context_`)
+- **Types**: Use `pb_byte_t`, `pb_size_t` for protobuf; `std::array`, `std::unique_ptr`
+- **Error Handling**: Return `TeslaBLE_Status_E` enum (0=OK); use `LOG_ERROR`/`LOG_DEBUG` macros
+- **Formatting**: No comments unless requested; 4-space indent; braces on same line
+- **Protobuf**: Use `*_init_default`/`*_init_zero`; encode with `pb_encode_fields`, decode with `pb_decode`