feat(llvm): Phase 134-A - mir_call.py unified 設計完成

681行の giant ファイルを機能別に分割し、箱化モジュール化を達成。

Changes:
- NEW: src/llvm_py/mir_call_compat.py (120 lines)
  - JSON v0/v1 互換層を一元管理
  - normalize_callee(), detect_format_version()

- NEW: src/llvm_py/instructions/mir_call/ (7 files)
  - __init__.py: Canonical Dispatcher (lower_mir_call)
  - global_call.py: Global関数呼び出し (90 lines)
  - method_call.py: Boxメソッド呼び出し (175 lines)
  - constructor_call.py: Boxコンストラクタ (122 lines)
  - closure_call.py: Closure生成 (87 lines)
  - value_call.py: 動的関数値呼び出し (112 lines)
  - extern_call.py: 外部C ABI呼び出し (135 lines)

- ARCHIVE: mir_call.py → mir_call_legacy.py

Technical Achievements:
✅ mir_call.py: 681行 → 分割（各 80-175行、責務 明確）
✅ Phase 133 ConsoleLlvmBridge パターンを継承
✅ NYASH_MIR_UNIFIED_CALL フラグ完全廃止
✅ legacy dispatcher 削除（NotImplementedError 根治）
✅ JSON v0/v1 互換層を mir_call_compat.py に一元化
✅ Fail-Fast 原則確立
✅ テスト: 全 mir_call 関連テスト PASS

Design Principles Inherited:
- Phase 133 ConsoleLlvmBridge 箱化パターン継承
- Each module has clear responsibility
- mir_call_compat.py で Phase 124+ v0削除が容易
- テスト分割で保守性大幅向上

Next Phase:
Phase 134-B - StringBox bridge 分離（boxcall.py:130-282）
Phase 134-C - CollectionBox bridge 分離（boxcall.py:325-375）

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

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

src/llvm_py/mir_call_compat.py

@@ -0,0 +1,120 @@
+"""
+JSON v0/v1 compatibility layer for MIR Call instructions.
+
+This module provides utilities to normalize JSON v0 and v1 formats
+for MIR Call instructions, making it easier to remove v0 in Phase 124+.
+
+JSON v0 format:
+    {"method": "log", "box_type": "ConsoleBox", "receiver": 42}
+
+JSON v1 format:
+    {"name": "log", "box_name": "ConsoleBox", "receiver": 42}
+"""
+
+from typing import Dict, Any, Optional
+
+
+class MirCallCompat:
+    """JSON v0/v1 compatibility processor for MIR Call instructions."""
+
+    @staticmethod
+    def normalize_callee(callee_json: Dict[str, Any]) -> Dict[str, Any]:
+        """
+        Normalize JSON v0/v1 callee format to unified internal format.
+
+        Args:
+            callee_json: Callee dict from MIR Call instruction
+
+        Returns:
+            Normalized dict with consistent keys:
+            {
+                "type": "Global" | "Method" | "Constructor" | "Closure" | "Value" | "Extern",
+                "name": str (function/method name),
+                "box_name": str (for Method/Constructor),
+                "receiver": int (for Method),
+                ... other fields
+            }
+
+        Examples:
+            v0: {"method": "log", "box_type": "ConsoleBox"}
+            v1: {"name": "log", "box_name": "ConsoleBox"}
+            → {"type": "Method", "name": "log", "box_name": "ConsoleBox"}
+        """
+        if not callee_json:
+            return {}
+
+        # Extract type (should already be present in both v0/v1)
+        callee_type = callee_json.get("type")
+
+        # Normalize method/function name (v0: "method", v1: "name")
+        name = callee_json.get("name") or callee_json.get("method")
+
+        # Normalize box type name (v0: "box_type", v1: "box_name")
+        box_name = callee_json.get("box_name") or callee_json.get("box_type")
+
+        # Build normalized result
+        normalized = {
+            "type": callee_type,
+        }
+
+        if name is not None:
+            normalized["name"] = name
+
+        if box_name is not None:
+            normalized["box_name"] = box_name
+
+        # Copy other fields as-is
+        for key in ["receiver", "value", "params", "captures", "me_capture", "certainty"]:
+            if key in callee_json:
+                normalized[key] = callee_json[key]
+
+        return normalized
+
+    @staticmethod
+    def detect_format_version(callee_json: Dict[str, Any]) -> int:
+        """
+        Detect whether callee JSON is v0 or v1 format.
+
+        Args:
+            callee_json: Callee dict from MIR Call instruction
+
+        Returns:
+            0 for v0 format (uses "method"/"box_type")
+            1 for v1 format (uses "name"/"box_name")
+
+        Raises:
+            ValueError: If format cannot be determined
+        """
+        if not callee_json:
+            raise ValueError("Empty callee JSON")
+
+        # Check for v0 markers
+        if "method" in callee_json or "box_type" in callee_json:
+            return 0
+
+        # Check for v1 markers
+        if "name" in callee_json or "box_name" in callee_json:
+            return 1
+
+        # No clear markers - check callee type
+        if callee_json.get("type") in ["Global", "Method", "Constructor", "Extern"]:
+            # Modern format (v1)
+            return 1
+
+        raise ValueError(f"Unknown callee format: {callee_json}")
+
+    @staticmethod
+    def is_v0_format(callee_json: Dict[str, Any]) -> bool:
+        """Check if callee JSON uses v0 format."""
+        try:
+            return MirCallCompat.detect_format_version(callee_json) == 0
+        except ValueError:
+            return False
+
+    @staticmethod
+    def is_v1_format(callee_json: Dict[str, Any]) -> bool:
+        """Check if callee JSON uses v1 format."""
+        try:
+            return MirCallCompat.detect_format_version(callee_json) == 1
+        except ValueError:
+            return False