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/subagent/event.rs

@@ -3,25 +3,22 @@ use serde_json::Value;
 #[derive(Debug, Clone)]
 pub enum SubagentEvent {
     StepCompleted {
-        step: usize,
-        output: String,
+        _step: usize,
+        _output: String,
     },
     StepFailed {
-        step: usize,
-        error: String,
+        _step: usize,
+        _error: String,
     },
     Completed {
-        output: String,
-    },
-    Failed {
-        error: String,
+        _output: String,
     },
     ToolCall {
-        tool: String,
-        args: Value,
+        _tool: String,
+        _args: Value,
     },
     ToolResult {
-        tool: String,
-        output: String,
+        _tool: String,
+        _output: String,
     },
 }