fix(mir): Phase 25.1m - Continue PHI修正 & Bug A main(args)ループ修正

**Phase 25.1m: Continue PHI修正**
- seal_phis に continue_snapshots 入力を追加 (loopform_builder.rs)
- LoopShape::debug_validate に continue/break エッジ検証追加 (control_form.rs)
- test_seal_phis_includes_continue_snapshots テスト追加
- 実証テスト成功: balanced scan loop で 228回イテレーション確認

**Bug A修正: main(args) でループ未実行問題**
- LoopBuilder::build_loop で entry → preheader への jump 追加
- decls.rs でデュアル関数作成時のブロック接続修正
- mir_static_main_args_loop.rs テスト追加

**パーサー改善**:
- parser_box.hako に HAKO_PARSER_PROG_MAX ガード追加（無限ループ対策）

🎉 成果:
- Continue 文の PHI predecessor mismatch エラー完全解消
- main(args) パラメータ有りループが正常動作
- Stage-B balanced scan で continue 正常動作確認 (228回イテレーション)

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

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

src/mir/builder/stmts.rs

@@ -152,11 +152,17 @@ impl super::MirBuilder {
         let scope_id = self.current_block.map(|bb| bb.as_u32()).unwrap_or(0);
         self.hint_scope_enter(scope_id);
         let mut last_value = None;
-        for statement in statements {
+        let total = statements.len();
+        eprintln!("[DEBUG/build_block] Processing {} statements", total);
+        for (idx, statement) in statements.into_iter().enumerate() {
+            eprintln!("[DEBUG/build_block] Statement {}/{}  current_block={:?}  current_function={}",
+                idx+1, total, self.current_block,
+                self.current_function.as_ref().map(|f| f.signature.name.as_str()).unwrap_or("none"));
             last_value = Some(self.build_statement(statement)?);
             // If the current block was terminated by this statement (e.g., return/throw),
             // do not emit any further instructions for this block.
             if is_current_block_terminated(self)? {
+                eprintln!("[DEBUG/build_block] Block terminated after statement {}", idx+1);
                 break;
             }
         }
@@ -168,6 +174,7 @@ impl super::MirBuilder {
         if !self.is_current_block_terminated() {
             self.hint_scope_leave(scope_id);
         }
+        eprintln!("[DEBUG/build_block] Completed, returning value {:?}", out);
         Ok(out)
     }