refactor(registry): simplify process registration

- Remove unused child parameter from register_agent_process()
- Simplify ProcessInfo structure by removing unnecessary process handle

src-tauri/src/process/registry.rs

@@ -93,7 +93,6 @@ impl ProcessRegistry {
         project_path: String,
         task: String,
         model: String,
-        child: tauri_plugin_shell::process::Child,
     ) -> Result<(), String> {
         let process_info = ProcessInfo {
             run_id,