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/runtime/event_loop/mod.rs

@@ -0,0 +1,52 @@
+use std::collections::VecDeque;
+use std::time::{Duration, Instant};
+
+use crate::app::state::runtime::TurnEvent;
+
+const FAST_POLL_MS: u64 = 8;
+const SLOW_POLL_MS: u64 = 100;
+const IDLE_THRESHOLD_MS: u64 = 500;
+
+pub struct EventLoop {
+    last_activity: Instant,
+    fast_poll_until: Option<Instant>,
+}
+
+impl EventLoop {
+    pub fn new() -> Self {
+        EventLoop {
+            last_activity: Instant::now(),
+            fast_poll_until: None,
+        }
+    }
+
+    pub fn poll_interval(&self) -> Duration {
+        if let Some(fast_until) = self.fast_poll_until {
+            if Instant::now() < fast_until {
+                return Duration::from_millis(FAST_POLL_MS);
+            }
+        }
+        Duration::from_millis(SLOW_POLL_MS)
+    }
+
+    pub fn mark_active(&mut self) {
+        self.last_activity = Instant::now();
+        self.fast_poll_until = Some(Instant::now() + Duration::from_millis(IDLE_THRESHOLD_MS));
+    }
+
+    pub fn is_idle(&self) -> bool {
+        self.last_activity.elapsed().as_millis() as u64 > IDLE_THRESHOLD_MS
+    }
+
+    pub fn drain_events(
+        events: &std::sync::Mutex<VecDeque<TurnEvent>>,
+    ) -> Vec<TurnEvent> {
+        events.lock().map(|mut q| q.drain(..).collect()).unwrap_or_default()
+    }
+}
+
+impl Default for EventLoop {
+    fn default() -> Self {
+        Self::new()
+    }
+}