[Feature] 添加 `/summary` 命令，生成会话工具调用摘要 / Add `/summary` command to generate session tool call summary

[SunYanbox]

该功能尚未实现 / This feature is not yet implemented.

需求描述 / Description

需要提供一个 /summary 命令，用于生成当前会话中调用工具情况的摘要。 / Provide a /summary command that generates a summary of tool call activities in the current session.

核心功能 / Core Features

• 按文件分组：按文件生成这些文件在工作区内被哪些工具读取/修改过。 / Group by file: For each file in the workspace, show which tools have read or modified it.
• 最新快照信息：提供每个文件最新的部分快照信息（如最近一次读取/修改的内容片段）。 / Latest snapshot info: Provide a partial snapshot of the latest state for each file (e.g., the most recent read/modified content snippet).
• 支持 --full 参数：完全返回全部工具结果，并自动去重。例如，如果一个文件曾被完整读取过，就不需要返回其他工具在该文件中搜索/截取的结果。 / Support --full flag: Return full tool results with deduplication. For example, if a file has been fully read, results from other tools that searched/snipped within that file should be omitted.

示例 / Example

/summary

输出（简要摘要）/ Output (brief summary):

文件: src/main.rs
  读取: read_file (第5-20行)
  修改: replace_in_file (第10行)

文件: src/lib.rs
  读取: search_content (匹配 "fn test")
  最新快照: "fn test() -> bool { true }"

/summary --full

输出（完整去重后工具结果）/ Output (full deduplicated tool results):

文件: src/main.rs
  [完整读取] read_file: <完整内容>
  [修改] replace_in_file: <修改差异>

文件: src/lib.rs
  [完整读取] read_file: <完整内容>
  (无搜索片段输出，因已有完整读取)