feat!: v0.2.0 — ping-on-connect validation, try_connect, publish polish

- Add ping-on-connect handshake: all connect functions validate the device
  within 200ms, rejecting non-DongLoRa serial devices immediately
- Add try_connect() — non-blocking connect that errors instead of blocking
  forever when no USB device is present
- Add payload size validation in transmit() (max 256 bytes)
- Add ErrorCode: impl std::error::Error
- Fix drain_rx error handling (no longer swallows original error)
- Fix repository URL to github.com/donglora/client-rs
- Remove wire-level tag constants from top-level re-exports
- Add rust-version (MSRV 1.85), homepage, exclude fields to Cargo.toml
- Add examples/ping.rs
- Allow clippy unwrap/expect in test modules

README.md

@@ -1,24 +1,21 @@
 # DongLoRa Rust Client
 
 Rust client library for talking to a DongLoRa device — either directly
-over USB or through the [mux daemon](../../mux/).
+over USB or through a mux daemon.
 
-## What's in Here
+## Install
 
-- `src/protocol.rs` — wire protocol types (`RadioConfig`, `Command`, `Response`, `ErrorCode`)
-- `src/codec.rs` — COBS framing, frame accumulator
-- `src/discovery.rs` — USB VID:PID device discovery
-- `src/transport.rs` — serial and mux socket transports
-- `src/client.rs` — high-level `Client<T>` with send/recv
-- `src/connect.rs` — auto-detection (mux socket, TCP, direct USB)
+```toml
+[dependencies]
+donglora-client = "0.2"
+```
 
-## Usage
+## Quick Start
 
 ```rust
 use donglora_client::*;
 
 let mut client = connect_default()?;
-client.ping()?;
 client.set_config(RadioConfig::default())?;
 client.start_rx()?;
 
@@ -29,6 +26,29 @@ loop {
 }
 ```
 
+All `connect` functions automatically validate the device by pinging it,
+so you'll get a clear error immediately if the port isn't a real DongLoRa.
+
+## What's in Here
+
+- `src/protocol.rs` — wire protocol types (`RadioConfig`, `Command`, `Response`, `ErrorCode`)
+- `src/codec.rs` — COBS framing, frame accumulator
+- `src/discovery.rs` — USB VID:PID device discovery
+- `src/transport.rs` — serial and mux socket transports
+- `src/client.rs` — high-level `Client<T>` with send/recv
+- `src/connect.rs` — auto-detection (mux socket, TCP, direct USB)
+
+## Connection Priority
+
+[`connect`] and [`try_connect`] try these in order:
+
+1. **TCP mux** — via `DONGLORA_MUX_TCP` env var
+2. **Unix socket mux** — checks `$XDG_RUNTIME_DIR/donglora/mux.sock` or `/tmp/donglora-mux.sock`
+3. **Direct USB serial** — auto-detects by VID:PID
+
+`try_connect` returns an error immediately if no device is found.
+`connect` blocks until a USB device appears.
+
 ## Dependencies
 
 - `ucobs` — COBS framing (same implementation as the firmware)