feat(session): Phase 4 - 斜杠命令完善

新增命令：
- /sessions — 列出 channel:chat_id 下最近 10 条对话
- /switch <dialog_id> — 切换到指定对话
- /rename <新标题> — 重命名当前对话

更新命令：
- /delete — 软删除后创建新对话
- /info — 显示 session_id + message_count

所有命令描述改为中文。

src/session/session.rs

@@ -605,27 +605,42 @@ impl SlashCommand {
 pub static SLASH_COMMANDS: &[SlashCommand] = &[
     SlashCommand {
         name: "new",
-        description: "Create a new conversation",
+        description: "创建新对话",
         aliases: &["/new"],
     },
+    SlashCommand {
+        name: "sessions",
+        description: "列出最近对话",
+        aliases: &["/sessions"],
+    },
+    SlashCommand {
+        name: "switch",
+        description: "切换到指定对话",
+        aliases: &["/switch"],
+    },
+    SlashCommand {
+        name: "rename",
+        description: "重命名当前对话",
+        aliases: &["/rename"],
+    },
     SlashCommand {
         name: "delete",
-        description: "Delete current conversation and start a new one",
+        description: "删除当前对话",
         aliases: &["/delete"],
     },
     SlashCommand {
         name: "compact",
-        description: "Manually trigger context compression",
+        description: "手动触发上下文压缩",
         aliases: &["/compact"],
     },
     SlashCommand {
         name: "info",
-        description: "Print current session information",
+        description: "显示当前对话信息",
         aliases: &["/info"],
     },
     SlashCommand {
         name: "dump",
-        description: "Save current session as markdown document",
+        description: "保存当前对话为 markdown 文档",
         aliases: &["/dump"],
     },
 ];
@@ -779,6 +794,36 @@ impl SessionManager {
                     Ok((None, "No active session.".to_string()))
                 }
             }
+            "sessions" => {
+                let (dialogs, _current) = self.list_dialogs(channel, chat_id, false).await?;
+                if dialogs.is_empty() {
+                    Ok((None, "暂无对话记录。".to_string()))
+                } else {
+                    let lines: Vec<String> = dialogs.iter().map(|d| {
+                        let current = if current_session_id.map(|s| s.dialog_id == d.session_id.dialog_id).unwrap_or(false) {
+                            " [当前]"
+                        } else {
+                            ""
+                        };
+                        format!("- {} ({}){} — {}", d.session_id.dialog_id, d.title, current, chrono::DateTime::from_timestamp_millis(d.last_active_at).map(|dt| dt.format("%m-%d %H:%M").to_string()).unwrap_or_default())
+                    }).collect();
+                    Ok((None, format!("最近对话：\n{}", lines.join("\n"))))
+                }
+            }
+            "switch" => {
+                let dialog_id = args.ok_or_else(|| AgentError::Other("Usage: /switch <dialog_id>".to_string()))?;
+                let new_id = self.switch_dialog(channel, chat_id, dialog_id).await?;
+                Ok((None, format!("已切换到对话：{}", new_id.dialog_id)))
+            }
+            "rename" => {
+                let title = args.ok_or_else(|| AgentError::Other("Usage: /rename <新标题>".to_string()))?;
+                if let Some(sid) = current_session_id {
+                    self.rename_dialog(sid, title).await?;
+                    Ok((None, format!("对话已重命名为：{}", title)))
+                } else {
+                    Ok((None, "No active session.".to_string()))
+                }
+            }
             _ => Err(AgentError::Other(format!("Command not implemented: {}", cmd.name))),
         }
     }