fix(session): 消息持久化和恢复

问题：消息只写内存，重启后丢失。from_storage 恢复了 meta 但没加载消息。

修复：
- add_message 改为 async，同时写内存和 Storage
- compact 场景用 persist=false 避免重复持久化
- clear_session_history 同时清内存和 Storage 消息
- 所有调用点添加 .await 和错误转换

src/session/session.rs

@@ -163,27 +163,9 @@ impl Session {
         self.id.to_string()
     }
 
-    /// 添加消息到历史（仅内存，Phase 3 会扩展为持久化）
-    pub fn add_message(&mut self, message: ChatMessage) {
-        let is_user = message.role == "user";
-        let now = chrono::Utc::now().timestamp_millis();
-
-        // Assign seq (in-memory only, persistence in Phase 3)
-        let _seq = self.seq_counter;
-        self.seq_counter += 1;
-
-        // Update in-memory state
-        self.messages.push(message);
-        self.total_message_count += 1;
-        if is_user {
-            self.message_count += 1;
-        }
-        self.last_active_at = now;
-    }
-
-    /// 添加消息到历史并持久化到 Storage（Phase 3 使用）
-    /// 目前 storage 为 None，此方法退化为 add_message
-    pub async fn add_message_and_persist(&mut self, message: ChatMessage) -> Result<(), StorageError> {
+    /// 添加消息到历史并持久化到 Storage
+    /// 如果 `persist` 为 false，只更新内存（用于 compaction 场景）
+    pub async fn add_message(&mut self, message: ChatMessage, persist: bool) -> Result<(), StorageError> {
         let is_user = message.role == "user";
         let now = chrono::Utc::now().timestamp_millis();
 
@@ -191,7 +173,8 @@ impl Session {
         let seq = self.seq_counter;
         self.seq_counter += 1;
 
-        // Persist to Storage (currently None, wired up in Phase 3)
+        // Persist to Storage
+        if persist {
             if let Some(ref storage) = self.storage {
                 let msg_meta = crate::storage::message::MessageMeta {
                     id: message.id.clone(),
@@ -211,6 +194,7 @@ impl Session {
                 };
                 storage.append_message_with_retry(&self.id.to_string(), &msg_meta).await?;
             }
+        }
 
         // Update in-memory state
         self.messages.push(message);
@@ -757,7 +741,8 @@ impl SessionManager {
                     let compressed_count = compressed.len();
                     session_guard.clear_history();
                     for msg in compressed {
-                        session_guard.add_message(msg);
+                        session_guard.add_message(msg, false).await
+                            .map_err(|e| AgentError::Other(format!("persist error: {}", e)))?;
                     }
                     Ok((None, format!(
                         "Context compressed: {} → {} messages.",
@@ -1125,7 +1110,8 @@ impl SessionManager {
             }
 
             let user_message = session_guard.create_user_message(content, media_refs);
-            session_guard.add_message(user_message);
+            session_guard.add_message(user_message, true).await
+                .map_err(|e| AgentError::Other(format!("persist error: {}", e)))?;
 
             let mut history = session_guard.get_history().to_vec();
 
@@ -1145,7 +1131,8 @@ impl SessionManager {
             let result = agent.process(history).await?;
 
             for msg in result.emitted_messages {
-                session_guard.add_message(msg);
+                session_guard.add_message(msg, true).await
+                    .map_err(|e| AgentError::Other(format!("persist error: {}", e)))?;
             }
 
             result.final_response.content
@@ -1165,7 +1152,16 @@ impl SessionManager {
     pub async fn clear_session_history(&self, unified_id: &UnifiedSessionId) -> Result<(), AgentError> {
         let session = self.get_or_create_session(unified_id).await?;
         let mut session_guard = session.lock().await;
-        session_guard.clear_history();
+        // Clear in-memory
+        session_guard.messages.clear();
+        session_guard.seq_counter = 1;
+        session_guard.total_message_count = 0;
+        session_guard.message_count = 0;
+        // Clear Storage
+        if let Some(ref storage) = session_guard.storage {
+            storage.clear_messages(&session_guard.id.to_string()).await
+                .map_err(|e| AgentError::Other(format!("failed to clear messages: {}", e)))?;
+        }
         Ok(())
     }
 }