🧹 refactor: box_methods.rs大掃除完全成功 - 8モジュールに機能分離

🏗️ アーキテクチャ大幅改善:
• 1822行巨大ファイル → 8つの論理的モジュールに完全分割
• 機能別責任分離でメンテナンス性向上
• ゼロ破壊的変更 - 既存機能すべて正常動作

📂 新モジュール構造:
• basic_methods.rs - StringBox/IntegerBox/BoolBox/FloatBox
• collection_methods.rs - ArrayBox/MapBox
• io_methods.rs - FileBox/ResultBox
• system_methods.rs - TimeBox/DateTimeBox/TimerBox/DebugBox
• math_methods.rs - MathBox/RandomBox
• async_methods.rs - FutureBox/ChannelBox
• web_methods.rs - WebDisplayBox/WebConsoleBox/WebCanvasBox(WASM)
• special_methods.rs - MethodBox/SoundBox

✨ コード品質向上:
• 可読性 - 機能別分離で理解容易
• 保守性 - 変更影響の局所化
• 拡張性 - 新機能追加が簡単
• テスト性 - 単体テスト作成容易

🎯 プロフェッショナルレベルのコードベース完成\!
Everything is Box哲学の美しい実装構造達成

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/interpreter/methods/io_methods.rs

@@ -0,0 +1,107 @@
+/*!
+ * I/O Operations Box Methods Module
+ * 
+ * Extracted from box_methods.rs
+ * Contains method implementations for I/O and error handling operations:
+ * - FileBox (execute_file_method) - File I/O operations
+ * - ResultBox (execute_result_method) - Error handling and result operations
+ */
+
+use super::super::*;
+use crate::box_trait::{FileBox, ResultBox, StringBox, NyashBox};
+
+impl NyashInterpreter {
+    /// FileBoxのメソッド呼び出しを実行
+    /// Handles file I/O operations including read, write, exists, delete, and copy
+    pub(in crate::interpreter) fn execute_file_method(&mut self, file_box: &FileBox, method: &str, arguments: &[ASTNode]) 
+        -> Result<Box<dyn NyashBox>, RuntimeError> {
+        match method {
+            "read" => {
+                if !arguments.is_empty() {
+                    return Err(RuntimeError::InvalidOperation {
+                        message: format!("read() expects 0 arguments, got {}", arguments.len()),
+                    });
+                }
+                Ok(file_box.read())
+            }
+            "write" => {
+                if arguments.len() != 1 {
+                    return Err(RuntimeError::InvalidOperation {
+                        message: format!("write() expects 1 argument, got {}", arguments.len()),
+                    });
+                }
+                let content = self.execute_expression(&arguments[0])?;
+                Ok(file_box.write(content))
+            }
+            "exists" => {
+                if !arguments.is_empty() {
+                    return Err(RuntimeError::InvalidOperation {
+                        message: format!("exists() expects 0 arguments, got {}", arguments.len()),
+                    });
+                }
+                Ok(file_box.exists())
+            }
+            "delete" => {
+                if !arguments.is_empty() {
+                    return Err(RuntimeError::InvalidOperation {
+                        message: format!("delete() expects 0 arguments, got {}", arguments.len()),
+                    });
+                }
+                Ok(file_box.delete())
+            }
+            "copy" => {
+                if arguments.len() != 1 {
+                    return Err(RuntimeError::InvalidOperation {
+                        message: format!("copy() expects 1 argument, got {}", arguments.len()),
+                    });
+                }
+                let dest_value = self.execute_expression(&arguments[0])?;
+                if let Some(dest_str) = dest_value.as_any().downcast_ref::<StringBox>() {
+                    Ok(file_box.copy(&dest_str.value))
+                } else {
+                    Err(RuntimeError::TypeError {
+                        message: "copy() requires string destination path".to_string(),
+                    })
+                }
+            }
+            _ => Err(RuntimeError::InvalidOperation {
+                message: format!("Unknown method '{}' for FileBox", method),
+            })
+        }
+    }
+
+    /// ResultBoxのメソッド呼び出しを実行
+    /// Handles result/error checking operations for error handling patterns
+    pub(in crate::interpreter) fn execute_result_method(&mut self, result_box: &ResultBox, method: &str, arguments: &[ASTNode]) 
+        -> Result<Box<dyn NyashBox>, RuntimeError> {
+        match method {
+            "isOk" => {
+                if !arguments.is_empty() {
+                    return Err(RuntimeError::InvalidOperation {
+                        message: format!("isOk() expects 0 arguments, got {}", arguments.len()),
+                    });
+                }
+                Ok(result_box.is_ok())
+            }
+            "getValue" => {
+                if !arguments.is_empty() {
+                    return Err(RuntimeError::InvalidOperation {
+                        message: format!("getValue() expects 0 arguments, got {}", arguments.len()),
+                    });
+                }
+                Ok(result_box.get_value())
+            }
+            "getError" => {
+                if !arguments.is_empty() {
+                    return Err(RuntimeError::InvalidOperation {
+                        message: format!("getError() expects 0 arguments, got {}", arguments.len()),
+                    });
+                }
+                Ok(result_box.get_error())
+            }
+            _ => Err(RuntimeError::InvalidOperation {
+                message: format!("Unknown method '{}' for ResultBox", method),
+            })
+        }
+    }
+}