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/app/state/runtime.rs

@@ -109,15 +109,4 @@ impl SessionRuntime {
     pub fn push_message(&mut self, msg: crate::dto::chat::message::ChatMessage) {
         self.messages.push(msg);
     }
-
-    pub fn record_api_call(&mut self, tokens_in: u64, tokens_out: u64, duration_ms: u64) {
-        self.usage.tokens_in += tokens_in;
-        self.usage.tokens_out += tokens_out;
-        self.usage.api_calls += 1;
-        self.usage.total_ms += duration_ms;
-    }
-
-    pub fn record_review_tokens(&mut self, tokens: u64) {
-        self.usage.review_tokens += tokens;
-    }
 }