Normalize passes keep spans and clean warnings

src/mir/builder/exprs_peek.rs

@@ -119,7 +119,13 @@ impl super::MirBuilder {
         self.start_new_block(merge_block)?;
         // フェーズM: PHI はブロック先頭に配置（cf_common 統一）
         if let (Some(func), Some(cur_bb)) = (self.current_function.as_mut(), self.current_block) {
-            crate::mir::ssot::cf_common::insert_phi_at_head(func, cur_bb, result_val, phi_inputs);
+            crate::mir::ssot::cf_common::insert_phi_at_head_spanned(
+                func,
+                cur_bb,
+                result_val,
+                phi_inputs,
+                self.current_span,
+            );
         } else {
             self.emit_instruction(super::MirInstruction::Phi {
                 dst: result_val,