refactor: apply zero-unwrap policy and optimize locks in store.rs and handlers

server/src/state.rs

@@ -62,7 +62,6 @@ impl MemoryState {
 
     pub async fn rebuild_index(&self) {
         if let Ok(new_idx) = MemoryIndex::new(&self.base_dir) {
-            
             let entities = self.graph.read().entities.into_values().collect();
             let tasks = self.tasks.read();
             let snippets = self.snippets.read();