refactor(baseliner): Replace shared Mutex state with thread-safe control snapshots

Eliminate lock contention between the baseliner, ratecontroller, and selector by moving to a message-passing architecture using immutable snapshots of reflector state. This improves data consistency and simplifies cross-thread communication.

src/util.rs

@@ -5,7 +5,6 @@
 use anyhow::anyhow;
 use std::sync::{Arc, Mutex, MutexGuard, RwLock, RwLockReadGuard, RwLockWriteGuard};
 
-pub type ArcMutex<T> = Arc<Mutex<T>>;
 pub type ArcRwLock<T> = Arc<RwLock<T>>;
 
 pub trait MutexExt<T> {