Refactor IPC and DTO structures; remove unused code and streamline message handling

- Removed unused structs and methods from `response.rs`, `usage.rs`, and `client.rs`.
- Simplified `Connection` handling in `conn.rs` to only support Unix sockets.
- Updated `IpcServer` to exclusively use Unix sockets and removed TCP handling.
- Cleaned up `editlog.rs` by removing loading and recent entry methods.
- Refactored `memory.rs` to eliminate unused functions related to lesson promotion and retrospective creation.
- Enhanced `search.rs` to support multiple search providers and improved error handling.
- Updated chat view logic to simplify message display and improve user experience.
- Removed deprecated modules and constants from various files to streamline the codebase.

src/ipc/conn.rs

@@ -1,38 +1,28 @@
-use std::net::TcpStream;
 use std::os::unix::net::UnixStream;
 use anyhow::Result;
 use super::frame;
 
-pub enum Connection {
-    Tcp(TcpStream),
-    Unix(UnixStream),
+pub struct Connection {
+    inner: UnixStream,
 }
 
 impl Connection {
-    pub fn connect_tcp(addr: &str) -> Result<Self> {
-        let stream = TcpStream::connect(addr)?;
-        stream.set_nodelay(true)?;
-        Ok(Connection::Tcp(stream))
+    pub fn from_stream(stream: UnixStream) -> Result<Self> {
+        Ok(Connection { inner: stream })
     }
 
     pub fn connect_unix(path: &str) -> Result<Self> {
         let stream = UnixStream::connect(path)?;
-        Ok(Connection::Unix(stream))
+        Ok(Connection { inner: stream })
     }
 
     pub fn send<T: serde::Serialize>(&mut self, value: &T) -> Result<()> {
         let data = frame::serialize_frame(value)?;
-        match self {
-            Connection::Tcp(ref mut s) => frame::write_frame(s, &data),
-            Connection::Unix(ref mut s) => frame::write_frame(s, &data),
-        }
+        frame::write_frame(&mut self.inner, &data)
     }
 
     pub fn receive<T: serde::de::DeserializeOwned>(&mut self) -> Result<Option<T>> {
-        let data = match self {
-            Connection::Tcp(ref mut s) => frame::read_frame(s)?,
-            Connection::Unix(ref mut s) => frame::read_frame(s)?,
-        };
+        let data = frame::read_frame(&mut self.inner)?;
         match data {
             Some(bytes) => {
                 let value: T = frame::deserialize_frame(&bytes)?;
@@ -41,17 +31,4 @@ impl Connection {
             None => Ok(None),
         }
     }
-
-    pub fn try_clone(&self) -> Result<Self> {
-        match self {
-            Connection::Tcp(s) => {
-                let cloned = s.try_clone()?;
-                Ok(Connection::Tcp(cloned))
-            }
-            Connection::Unix(s) => {
-                let cloned = s.try_clone()?;
-                Ok(Connection::Unix(cloned))
-            }
-        }
-    }
 }