feat(mcp): 增加游戏内方块调试桥接

新增 stdio MCP server 和 mcp 子命令，通过调试会话状态文件连接内置 TCP bridge，并提供 place_block 工具。

Bridge 将请求投递到服务端 System 的游戏线程执行，限制请求大小与队列长度，并按会话端口安全清理状态文件和连接。

src/debug/process.rs

@@ -40,6 +40,7 @@ pub fn launch_game(
     config: &DebugConfig,
     config_arg: Option<&Path>,
     mod_dirs: &[ResolvedModDir],
+    mcp_state_path: Option<&Path>,
 ) -> Result<()> {
     let enable_ipc = config.auto_hot_reload_mods;
     let ipc = if enable_ipc {
@@ -52,9 +53,10 @@ pub fn launch_game(
 
     let command = build_command(config, config_arg);
     let mut command_w = wide_null(OsStr::new(&command));
-    let env_block = if ipc.is_some() || config.auto_hot_reload_ui {
+    let env_block = if ipc.is_some() || mcp_state_path.is_some() || config.auto_hot_reload_ui {
         Some(build_environment_block(
             ipc.as_ref().map(|server| server.port()),
+            mcp_state_path,
         ))
     } else {
         None
@@ -154,6 +156,7 @@ pub fn launch_game(
     _config: &DebugConfig,
     _config_arg: Option<&Path>,
     _mod_dirs: &[ResolvedModDir],
+    _mcp_state_path: Option<&Path>,
 ) -> Result<()> {
     Err(CliError::InvalidInput(
         "debug launch is only supported on Windows".to_string(),
@@ -230,11 +233,12 @@ where
 }
 
 #[cfg(windows)]
-fn build_environment_block(ipc_port: Option<u16>) -> Vec<u16> {
+fn build_environment_block(ipc_port: Option<u16>, mcp_state_path: Option<&Path>) -> Vec<u16> {
     let mut pairs: Vec<(Vec<u16>, Vec<u16>)> = std::env::vars_os()
         .filter(|(key, _)| {
             let key = key.to_string_lossy();
             !key.eq_ignore_ascii_case("MCDEV_DEBUG_IPC_PORT")
+                && !key.eq_ignore_ascii_case("MCDEV_MCP_BRIDGE_STATE")
         })
         .map(|(key, value)| (key.encode_wide().collect(), value.encode_wide().collect()))
         .collect();
@@ -245,6 +249,13 @@ fn build_environment_block(ipc_port: Option<u16>) -> Vec<u16> {
             OsStr::new(&port.to_string()).encode_wide().collect(),
         ));
     }
+    if let Some(path) = mcp_state_path {
+        let state_path = path.to_string_lossy().replace('\\', "/");
+        pairs.push((
+            OsStr::new("MCDEV_MCP_BRIDGE_STATE").encode_wide().collect(),
+            OsStr::new(&state_path).encode_wide().collect(),
+        ));
+    }
     pairs.sort_by(|a, b| a.0.cmp(&b.0));
 
     let mut block = Vec::new();