feat(mir): Phase 25.1f完了 - Conservative PHI + ControlForm観測レイヤー

🎉 Conservative PHI Box理論による完全SSA構築

**Phase 7-B: Conservative PHI実装**
- 片方branchのみ定義変数に対応（emit_void使用）
- 全変数にPHI生成（Conservative Box理論）
- Stage-1 resolver全テスト緑化（3/3 PASS）

**Phase 25.1f: ControlForm観測レイヤー**
- LoopShape/IfShape/ControlForm構造定義
- Loop/If統一インターフェース実装
- debug_dump/debug_validate機能追加
- NYASH_CONTROL_FORM_TRACE環境変数対応

**主な変更**:
- src/mir/builder/phi.rs: Conservative PHI実装
- src/mir/control_form.rs: ControlForm構造（NEW）
- src/mir/loop_builder.rs: LoopForm v2デフォルト化

**テスト結果**:
✅ mir_stage1_using_resolver_min_fragment_verifies
✅ mir_stage1_using_resolver_full_collect_entries_verifies
✅ mir_parserbox_parse_program2_harness_parses_minimal_source

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: ChatGPT <chatgpt@openai.com>

src/benchmarks.rs

@@ -33,7 +33,10 @@ impl BenchmarkSuite {
 
     /// Run comprehensive benchmark across all backends
     pub fn run_all(&self) -> Vec<BenchmarkResult> {
+        #[cfg(feature = "wasm-backend")]
         let mut results = Vec::new();
+        #[cfg(not(feature = "wasm-backend"))]
+        let results = Vec::new();
 
         let benchmarks = [
             ("bench_light", "benchmarks/bench_light.hako"),
@@ -45,14 +48,14 @@ impl BenchmarkSuite {
             println!("🚀 Running benchmark: {}", name);
 
             // Test if file exists and is readable
-            if let Ok(source) = fs::read_to_string(file_path) {
+            if let Ok(_source) = fs::read_to_string(file_path) {
                 // Run on all backends
                 // Interpreter benchmark removed with legacy interpreter
 
                 // VM benchmark removed with vm-legacy
 
                 #[cfg(feature = "wasm-backend")]
-                if let Ok(wasm_result) = self.run_wasm_benchmark(name, &source) {
+                if let Ok(wasm_result) = self.run_wasm_benchmark(name, &_source) {
                     results.push(wasm_result);
                 }
             } else {