refactor: 大規模ファイル分割とプラグインリファクタリング

## 🎯 プラグイン整理
- ✅ **nyash-json-plugin**: プロバイダー抽象化、NodeRep統一
- ✅ **nyash-string-plugin**: TLVヘルパー整理
- ✅ **nyash-net-plugin**: HTTPヘルパー分離、ソケット管理改善
- ✅ **nyash-counter-plugin/fixture-plugin**: 基本構造整理

## 📂 mir_interpreter分割
- ✅ **mir_interpreter.rs → mir_interpreter/ディレクトリ**
  - mod.rs: メイン構造体定義
  - execution.rs: 実行エンジン
  - memory.rs: メモリ管理
  - instructions/: 命令別実装

## 🔧 その他の改善
- テストファイル群の最適化
- LLVMコンパイラのメイン関数整理
- 不要なインポート削除

1000行超のファイルを適切なモジュール構造に分割完了！

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

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

src/backend/mir_interpreter/helpers.rs

@@ -0,0 +1,76 @@
+use super::*;
+
+impl MirInterpreter {
+    pub(super) fn reg_load(&self, id: ValueId) -> Result<VMValue, VMError> {
+        self.regs
+            .get(&id)
+            .cloned()
+            .ok_or_else(|| VMError::InvalidValue(format!("use of undefined value {:?}", id)))
+    }
+
+    pub(super) fn eval_binop(
+        &self,
+        op: BinaryOp,
+        a: VMValue,
+        b: VMValue,
+    ) -> Result<VMValue, VMError> {
+        use BinaryOp::*;
+        use VMValue::*;
+        Ok(match (op, a, b) {
+            (Add, Integer(x), Integer(y)) => Integer(x + y),
+            (Add, String(s), Integer(y)) => String(format!("{}{}", s, y)),
+            (Add, String(s), Float(y)) => String(format!("{}{}", s, y)),
+            (Add, String(s), Bool(y)) => String(format!("{}{}", s, y)),
+            (Add, String(s), String(t)) => String(format!("{}{}", s, t)),
+            (Add, Integer(x), String(t)) => String(format!("{}{}", x, t)),
+            (Add, Float(x), String(t)) => String(format!("{}{}", x, t)),
+            (Add, Bool(x), String(t)) => String(format!("{}{}", x, t)),
+            (Sub, Integer(x), Integer(y)) => Integer(x - y),
+            (Mul, Integer(x), Integer(y)) => Integer(x * y),
+            (Div, Integer(_), Integer(0)) => return Err(VMError::DivisionByZero),
+            (Div, Integer(x), Integer(y)) => Integer(x / y),
+            (Mod, Integer(_), Integer(0)) => return Err(VMError::DivisionByZero),
+            (Mod, Integer(x), Integer(y)) => Integer(x % y),
+            (Add, Float(x), Float(y)) => Float(x + y),
+            (Sub, Float(x), Float(y)) => Float(x - y),
+            (Mul, Float(x), Float(y)) => Float(x * y),
+            (Div, Float(_), Float(y)) if y == 0.0 => return Err(VMError::DivisionByZero),
+            (Div, Float(x), Float(y)) => Float(x / y),
+            (Mod, Float(x), Float(y)) => Float(x % y),
+            (BitAnd, Integer(x), Integer(y)) => Integer(x & y),
+            (BitOr, Integer(x), Integer(y)) => Integer(x | y),
+            (BitXor, Integer(x), Integer(y)) => Integer(x ^ y),
+            (Shl, Integer(x), Integer(y)) => Integer(x.wrapping_shl(y as u32)),
+            (Shr, Integer(x), Integer(y)) => Integer(x.wrapping_shr(y as u32)),
+            (opk, va, vb) => {
+                return Err(VMError::TypeError(format!(
+                    "unsupported binop {:?} on {:?} and {:?}",
+                    opk, va, vb
+                )))
+            }
+        })
+    }
+
+    pub(super) fn eval_cmp(&self, op: CompareOp, a: VMValue, b: VMValue) -> Result<bool, VMError> {
+        use CompareOp::*;
+        use VMValue::*;
+        Ok(match (op, &a, &b) {
+            (Eq, _, _) => eq_vm(&a, &b),
+            (Ne, _, _) => !eq_vm(&a, &b),
+            (Lt, Integer(x), Integer(y)) => x < y,
+            (Le, Integer(x), Integer(y)) => x <= y,
+            (Gt, Integer(x), Integer(y)) => x > y,
+            (Ge, Integer(x), Integer(y)) => x >= y,
+            (Lt, Float(x), Float(y)) => x < y,
+            (Le, Float(x), Float(y)) => x <= y,
+            (Gt, Float(x), Float(y)) => x > y,
+            (Ge, Float(x), Float(y)) => x >= y,
+            (opk, va, vb) => {
+                return Err(VMError::TypeError(format!(
+                    "unsupported compare {:?} on {:?} and {:?}",
+                    opk, va, vb
+                )))
+            }
+        })
+    }
+}