feat: 改行処理革命Phase 2-B完了 - Box宣言系skip_newlines()完全削除

✅ **41%削減達成**: 48→35→21箇所（14箇所削除）
- fields.rs: 9箇所のskip_newlines()削除
- box_definition.rs: 3箇所削除
- static_box.rs: 2箇所削除

✅ **Smart advance()実用化**: 深度追跡で自動改行処理完璧機能
- Box宣言、match式OR、複数行構文すべて対応
- NYASH_SMART_ADVANCE=1で安定動作確認

🔧 **ORパターンバグ同時修正**: exprs_peek.rsでInteger/Boolean型マッチング実装
- 修正前: 1 | 2 => "found" が動作せず（String型のみ）
- 修正後: 全リテラル型（Integer/Bool/Float/Null/Void）完全対応

🎉 **技術的価値**: 手動skip依存→コンテキスト認識自動処理への移行成功

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

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

src/mir/builder/exprs_peek.rs

@@ -75,25 +75,31 @@ impl super::MirBuilder {
 
             // In current dispatch block, compare and branch
             self.start_new_block(cur_dispatch)?;
-            if let LiteralValue::String(s) = label {
-                let lit_id = self.value_gen.next();
-                self.emit_instruction(super::MirInstruction::Const {
-                    dst: lit_id,
-                    value: super::ConstValue::String(s),
-                })?;
-                let cond_id = self.value_gen.next();
-                self.emit_instruction(super::MirInstruction::Compare {
-                    dst: cond_id,
-                    op: super::CompareOp::Eq,
-                    lhs: scr_val,
-                    rhs: lit_id,
-                })?;
-                self.emit_instruction(super::MirInstruction::Branch {
-                    condition: cond_id,
-                    then_bb: then_block,
-                    else_bb: else_target,
-                })?;
-            }
+            let lit_id = self.value_gen.next();
+            let const_value = match label {
+                LiteralValue::String(s) => super::ConstValue::String(s),
+                LiteralValue::Integer(i) => super::ConstValue::Integer(i),
+                LiteralValue::Bool(b) => super::ConstValue::Bool(b),
+                LiteralValue::Float(f) => super::ConstValue::Float(f),
+                LiteralValue::Null => super::ConstValue::Null,
+                LiteralValue::Void => super::ConstValue::Void,
+            };
+            self.emit_instruction(super::MirInstruction::Const {
+                dst: lit_id,
+                value: const_value,
+            })?;
+            let cond_id = self.value_gen.next();
+            self.emit_instruction(super::MirInstruction::Compare {
+                dst: cond_id,
+                op: super::CompareOp::Eq,
+                lhs: scr_val,
+                rhs: lit_id,
+            })?;
+            self.emit_instruction(super::MirInstruction::Branch {
+                condition: cond_id,
+                then_bb: then_block,
+                else_bb: else_target,
+            })?;
 
             // then arm
             self.start_new_block(then_block)?;