feat(phase33): mir_call.hako Stage 1 complete - unified Call instruction skeleton

Stage 1 Implementation (208 lines):
- 6 callee types: Global/Method/Constructor/Extern/Closure/Value
- CallEmitBox reuse: 60% of functionality already implemented
- JSON generation only (C++ backend handles LLVM IR)

Builder Integration:
- Added MirCallInst import and delegation methods
- 10 instructions complete: const, binop, compare, ret, branch, jump, copy, phi, loopform, mir_call

Tests (333 lines):
- Unit tests: 6 tests covering all callee types (288 lines)
- Smoke test: Global function call verification (45 lines)

Build Status:
- Rust build: SUCCESS (0 errors)
- Test execution: PENDING (Phase 33 environment setup required)

Code Reduction:
- Python mir_call.py: 641 lines
- Hakorune mir_call.hako: 208 lines
- Reduction: -67.5% (using existing CallEmitBox)

Next Steps:
- Stage 2-6: Complete implementation
- CallEmitBox.make_mir_call_closure/value additions
- C++ backend integration

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

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

lang/src/llvm_ir/boxes/builder.hako

@@ -7,6 +7,7 @@ using "../instructions/jump.hako" as JumpInst
 using "../instructions/copy.hako" as CopyInst
 using "../instructions/phi.hako" as PhiInst
 using "../instructions/loopform.hako" as LoopFormInst
+using "../instructions/mir_call.hako" as MirCallInst
 
 // LLVMBuilderBox — 命令構築（v0: const/binop/ret の骨格）
 static box LLVMBuilderBox {
@@ -389,4 +390,22 @@ static box LLVMBuilderBox {
   emit_loopform(self, loop_id, blocks, condition_vid, options) {
     return me.lower_loopform(self, loop_id, blocks, condition_vid, options)
   }
+
+  // Phase v2-C MIR Call 命令（統一Call）
+  // Args:
+  //   self: static box receiver (implicit)
+  //   callee: calleeオブジェクト {type: "Global|Method|Constructor|...", ...}
+  //   args: 引数配列（ArrayBox of register IDs）
+  //   dst: 結果レジスタID
+  //   options: オプション設定（省略可）
+  // Returns:
+  //   MIR Call JSON 文字列
+  lower_mir_call(self, callee, args, dst, options) {
+    return MirCallInst.lower_mir_call(self, callee, args, dst, options)
+  }
+
+  // MIR Call 命令を emit（builder メソッド）
+  emit_mir_call(self, callee, args, dst, options) {
+    return me.lower_mir_call(self, callee, args, dst, options)
+  }
 }