add all crates: domain, protocol, application, client, adapters, ESP32 firmware

Server: domain (entities, value objects, ports), protocol (postcard wire types),
application (config service, data projection), adapters (config-memory, tcp-server),
bootstrap (composition root with fake data).

Client: client-domain (layout engine, render tree, HAL ports),
client-application (message handling, repaint commands),
adapters (tcp-client, display-terminal), client-desktop (end-to-end working).

ESP32: client-esp32 firmware with ILI9341 display over SPI, WiFi networking.
Display test verified on hardware — landscape orientation, text rendering works.

60 workspace tests, all passing.

crates/adapters/tcp-client/src/lib.rs

@@ -0,0 +1,82 @@
+use std::io::{Read, Write};
+use std::net::TcpStream;
+use std::time::Duration;
+use client_domain::NetworkPort;
+use protocol::MAX_FRAME_SIZE;
+
+#[derive(Debug)]
+pub enum TcpClientError {
+    Io(std::io::Error),
+    NotConnected,
+    FrameTooLarge(usize),
+}
+
+impl std::fmt::Display for TcpClientError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            TcpClientError::Io(e) => write!(f, "io: {e}"),
+            TcpClientError::NotConnected => write!(f, "not connected"),
+            TcpClientError::FrameTooLarge(n) => write!(f, "frame too large: {n}"),
+        }
+    }
+}
+
+pub struct StdTcpClient {
+    stream: Option<TcpStream>,
+}
+
+impl StdTcpClient {
+    pub fn new() -> Self {
+        Self { stream: None }
+    }
+}
+
+impl NetworkPort for StdTcpClient {
+    type Error = TcpClientError;
+
+    fn connect(&mut self, addr: &str) -> Result<(), Self::Error> {
+        let stream = TcpStream::connect(addr).map_err(TcpClientError::Io)?;
+        stream.set_nonblocking(true).map_err(TcpClientError::Io)?;
+        stream.set_read_timeout(Some(Duration::from_millis(10))).map_err(TcpClientError::Io)?;
+        self.stream = Some(stream);
+        Ok(())
+    }
+
+    fn disconnect(&mut self) -> Result<(), Self::Error> {
+        self.stream = None;
+        Ok(())
+    }
+
+    fn send(&mut self, data: &[u8]) -> Result<(), Self::Error> {
+        let stream = self.stream.as_mut().ok_or(TcpClientError::NotConnected)?;
+        stream.write_all(data).map_err(TcpClientError::Io)
+    }
+
+    fn receive(&mut self) -> Result<Option<Vec<u8>>, Self::Error> {
+        let stream = self.stream.as_mut().ok_or(TcpClientError::NotConnected)?;
+
+        let mut len_buf = [0u8; 4];
+        match stream.read_exact(&mut len_buf) {
+            Ok(()) => {}
+            Err(e) if e.kind() == std::io::ErrorKind::WouldBlock => return Ok(None),
+            Err(e) if e.kind() == std::io::ErrorKind::TimedOut => return Ok(None),
+            Err(e) => return Err(TcpClientError::Io(e)),
+        }
+
+        let len = u32::from_be_bytes(len_buf) as usize;
+        if len > MAX_FRAME_SIZE {
+            return Err(TcpClientError::FrameTooLarge(len));
+        }
+
+        let mut payload = vec![0u8; len];
+        stream.set_nonblocking(false).map_err(TcpClientError::Io)?;
+        stream.read_exact(&mut payload).map_err(TcpClientError::Io)?;
+        stream.set_nonblocking(true).map_err(TcpClientError::Io)?;
+
+        Ok(Some(payload))
+    }
+
+    fn is_connected(&self) -> bool {
+        self.stream.is_some()
+    }
+}