fix(joinir): Phase 82-5 lifecycle.rs return type inference bug fix

**Problem**: lifecycle.rs walked bb.instructions before checking bb.terminator,
causing it to infer types from intermediate values like `%1 = const void` instead
of the actual return value.

**Solution**: Remove instructions walking entirely, only check terminator Returns.
This ensures we infer type from the actual return value (e.g., `ret %3`).

**Impact**:
- Case D failures: 51 → 20 (60% reduction! 31 eliminated)
- Removed ~55 lines of redundant instructions walking
- All remaining 20 Case D are genuine GenericTypeResolver coverage issues

**Files Modified**:
- src/mir/builder/lifecycle.rs: Remove instructions loop, only check terminator

**Test Results**:
- Baseline: 483 passed, 33 failed
- With NYASH_PHI_FALLBACK_DISABLED=1: 463 passed, 53 failed (20 Case D panics)
- All remaining Case D are in `main` functions (genuine, not bugs)

**Related**: Phase 82-if-phi-retire Step 5 (ChatGPT root cause analysis)

src/mir/builder/lifecycle.rs

@@ -301,68 +301,16 @@ impl super::MirBuilder {
         let mut module = self.current_module.take().unwrap();
         let mut function = self.current_function.take().unwrap();
         function.metadata.value_types = self.value_types.clone();
+        // Phase 82-5: lifecycle.rs バグ修正 - terminator の Return のみをチェック
+        //   問題: instructions を先に走査すると、中間値（const void 等）を誤って推論対象にしてしまう
+        //   解決: terminator の Return のみをチェックし、実際の戻り値を正しく推論する
         if matches!(
             function.signature.return_type,
             super::MirType::Void | super::MirType::Unknown
         ) {
             let mut inferred: Option<super::MirType> = None;
-            'outer: for (_bid, bb) in function.blocks.iter() {
-                for inst in bb.instructions.iter() {
-                    if let super::MirInstruction::Return { value: Some(v) } = inst {
-                        if let Some(mt) = self.value_types.get(v).cloned() {
-                            inferred = Some(mt);
-                            break 'outer;
-                        }
-                        // Phase 65.5: TypeHintPolicy 使用（箱化モジュール）
-                        // Phase 67: P3-C 経路を GenericTypeResolver に委譲
-                        let hint = if TypeHintPolicy::is_target(&function.signature.name) {
-                            TypeHintPolicy::extract_phi_type_hint(&function, *v)
-                        } else {
-                            None
-                        };
-                        // Phase 67: P3-C 対象なら GenericTypeResolver を優先使用
-                        if hint.is_none() && TypeHintPolicy::is_p3c_target(&function.signature.name)
-                        {
-                            if let Some(mt) = GenericTypeResolver::resolve_from_phi(
-                                &function,
-                                *v,
-                                &self.value_types,
-                            ) {
-                                if std::env::var("NYASH_P3C_DEBUG").is_ok() {
-                                    eprintln!(
-                                        "[lifecycle/p3c] {} type inferred via GenericTypeResolver: {:?}",
-                                        function.signature.name, mt
-                                    );
-                                }
-                                inferred = Some(mt);
-                                break 'outer;
-                            }
-                        }
-                        // Phase 82: dev ガード - if_phi フォールバック禁止モード
-                        if crate::config::env::phi_fallback_disabled() {
-                            let case =
-                                classify_phi_fallback_case(hint.as_ref(), &function.signature.name);
-                            panic!(
-                                "[phase82/phi_fallback] disabled but infer_type_from_phi called\n\
-                                 Function: {}\n\
-                                 ValueId: {:?}\n\
-                                 Case: {}",
-                                function.signature.name, v, case
-                            );
-                        }
-                        if let Some(mt) =
-                            crate::mir::phi_core::if_phi::infer_type_from_phi_with_hint(
-                                hint, // Phase 63-6-3: P1 の場合は PHI の type_hint、それ以外は None
-                                &function,
-                                *v,
-                                &self.value_types,
-                            )
-                        {
-                            inferred = Some(mt);
-                            break 'outer;
-                        }
-                    }
-                }
+            for (_bid, bb) in function.blocks.iter() {
+                // Phase 82-5: instructions 走査を削除、terminator の Return のみをチェック
                 if let Some(super::MirInstruction::Return { value: Some(v) }) = &bb.terminator {
                     if let Some(mt) = self.value_types.get(v).cloned() {
                         inferred = Some(mt);