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

src/transport.rs

@@ -61,9 +61,7 @@ impl Write for SerialTransport {
 
 impl Transport for SerialTransport {
     fn set_timeout(&mut self, timeout: Duration) -> anyhow::Result<()> {
-        self.port
-            .set_timeout(timeout)
-            .map_err(|e| anyhow::anyhow!("failed to set serial timeout: {e}"))?;
+        self.port.set_timeout(timeout).map_err(|e| anyhow::anyhow!("failed to set serial timeout: {e}"))?;
         self.timeout = timeout;
         Ok(())
     }
@@ -99,10 +97,7 @@ impl MuxTransport {
         stream
             .set_write_timeout(Some(timeout))
             .map_err(|e| anyhow::anyhow!("failed to set socket write timeout: {e}"))?;
-        Ok(Self {
-            stream: MuxStream::Unix(stream),
-            timeout,
-        })
+        Ok(Self { stream: MuxStream::Unix(stream), timeout })
     }
 
     /// Connect to the mux daemon via TCP.
@@ -117,16 +112,9 @@ impl MuxTransport {
             .ok_or_else(|| anyhow::anyhow!("no addresses found for {addr}"))?;
         let stream = std::net::TcpStream::connect_timeout(&sock_addr, timeout)
             .map_err(|e| anyhow::anyhow!("failed to connect to mux at {addr}: {e}"))?;
-        stream
-            .set_read_timeout(Some(timeout))
-            .map_err(|e| anyhow::anyhow!("failed to set TCP read timeout: {e}"))?;
-        stream
-            .set_write_timeout(Some(timeout))
-            .map_err(|e| anyhow::anyhow!("failed to set TCP write timeout: {e}"))?;
-        Ok(Self {
-            stream: MuxStream::Tcp(stream),
-            timeout,
-        })
+        stream.set_read_timeout(Some(timeout)).map_err(|e| anyhow::anyhow!("failed to set TCP read timeout: {e}"))?;
+        stream.set_write_timeout(Some(timeout)).map_err(|e| anyhow::anyhow!("failed to set TCP write timeout: {e}"))?;
+        Ok(Self { stream: MuxStream::Tcp(stream), timeout })
     }
 }
 
@@ -163,12 +151,8 @@ impl Transport for MuxTransport {
         self.timeout = timeout;
         let result = match &self.stream {
             #[cfg(unix)]
-            MuxStream::Unix(s) => s
-                .set_read_timeout(Some(timeout))
-                .and_then(|()| s.set_write_timeout(Some(timeout))),
-            MuxStream::Tcp(s) => s
-                .set_read_timeout(Some(timeout))
-                .and_then(|()| s.set_write_timeout(Some(timeout))),
+            MuxStream::Unix(s) => s.set_read_timeout(Some(timeout)).and_then(|()| s.set_write_timeout(Some(timeout))),
+            MuxStream::Tcp(s) => s.set_read_timeout(Some(timeout)).and_then(|()| s.set_write_timeout(Some(timeout))),
         };
         result.map_err(|e| anyhow::anyhow!("failed to set timeout: {e}"))
     }