refactor(joinir): Phase 85 - Quick wins: loop_patterns removal, DebugOutputBox, dead_code audit

Quick Win 1: Remove loop_patterns_old.rs (COMPLETED)
- Deleted obsolete legacy loop pattern dispatcher (914 lines)
- All patterns (Break/Continue/Simple) now in modular loop_patterns/ system
- Moved helper functions (has_break_in_loop_body, has_continue_in_loop_body) to analysis.rs
- Updated loop_frontend_binding.rs to remove fallback
- Verified zero regressions: 974/974 lib tests PASS

Quick Win 2: DebugOutputBox consolidation (COMPLETED)
- New module: src/mir/join_ir/lowering/debug_output_box.rs (170 lines)
- Centralized debug output management with automatic HAKO_JOINIR_DEBUG checking
- Refactored 4 files to use DebugOutputBox:
  - condition_env.rs: 3 scattered checks → 3 Box calls
  - carrier_binding_assigner.rs: 1 check → 1 Box call
  - scope_manager.rs: 3 checks → 3 Box calls
  - analysis.rs: Updated lower_loop_with_if_meta to use new pattern system
- Benefits: Consistent formatting, centralized control, zero runtime cost when disabled
- Added 4 unit tests for DebugOutputBox

Quick Win 3: Dead code directive audit (COMPLETED)
- Audited all 40 #[allow(dead_code)] directives in lowering/
- Findings: All legitimate (Phase utilities, future placeholders, API completeness)
- No unsafe removals needed
- Categories:
  - Phase 192 utilities (whitespace_check, entry_builder): Public API with tests
  - Phase 231 placeholders (expr_lowerer): Explicitly marked future use
  - Const helpers (value_id_ranges): API completeness
  - Loop metadata (loop_update_summary): Future phase fields

Result: Net -858 lines, improved code clarity, zero regressions
Tests: 974/974 PASS (gained 4 from DebugOutputBox tests)

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

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/mir/join_ir/frontend/ast_lowerer/analysis.rs

@@ -251,7 +251,7 @@ impl AstToJoinIrLowerer {
 
     /// Phase 40-1実験用: array_ext.filter パターン専用lowering
     ///
-    /// 通常の lower_loop_case_a_simple() に加えて、
+    /// 通常の Simple パターンループ lowering に加えて、
     /// if-in-loop modified varsをJoinFuncMetaMapとして返す。
     ///
     /// # Returns
@@ -260,14 +260,19 @@ impl AstToJoinIrLowerer {
     ///
     /// # Phase 40-1専用
     /// この関数はPhase 40-1 A/Bテスト専用。
-    /// 本番パスでは使わない（従来のlower_loop_case_a_simple()を使う）。
+    /// 本番パスでは使わない（新しいloop_patterns::simple::lower()を使う）。
+    ///
+    /// # Phase 85 Note
+    /// loop_patterns_old.rs削除に伴い、loop_patterns::simple::lower()に委譲
     #[allow(dead_code)]
     pub fn lower_loop_with_if_meta(
         &mut self,
         program_json: &serde_json::Value,
     ) -> (JoinModule, JoinFuncMetaMap) {
-        // 1. 通常のJoinModule生成（既存ロジック流用）
-        let module = self.lower_loop_case_a_simple(program_json);
+        // 1. 通常のJoinModule生成（新パターンシステムに委譲）
+        use super::loop_patterns;
+        let module = loop_patterns::simple::lower(self, program_json)
+            .expect("Simple pattern lowering failed in lower_loop_with_if_meta");
 
         // 2. loop body ASTからif-in-loop modified varsを抽出
         let loop_body = self.extract_loop_body_from_program(program_json);
@@ -339,4 +344,72 @@ impl AstToJoinIrLowerer {
         }
         vars
     }
+
+    /// Phase 85: Loop body に Break があるかチェック
+    ///
+    /// ループパターン検出（loop_frontend_binding）で使用される。
+    /// If文内のBreakステートメントを検出する。
+    ///
+    /// # Arguments
+    /// * `loop_body` - ループ本体のステートメント配列
+    ///
+    /// # Returns
+    /// ループ内にBreakがあればtrue
+    pub(crate) fn has_break_in_loop_body(loop_body: &[serde_json::Value]) -> bool {
+        loop_body.iter().any(|stmt| {
+            if stmt["type"].as_str() == Some("If") {
+                let then_has = stmt["then"]
+                    .as_array()
+                    .map(|body| {
+                        body.iter()
+                            .any(|s| s["type"].as_str() == Some("Break"))
+                    })
+                    .unwrap_or(false);
+                let else_has = stmt["else"]
+                    .as_array()
+                    .map(|body| {
+                        body.iter()
+                            .any(|s| s["type"].as_str() == Some("Break"))
+                    })
+                    .unwrap_or(false);
+                then_has || else_has
+            } else {
+                false
+            }
+        })
+    }
+
+    /// Phase 85: Loop body に Continue があるかチェック
+    ///
+    /// ループパターン検出（loop_frontend_binding）で使用される。
+    /// If文内のContinueステートメントを検出する。
+    ///
+    /// # Arguments
+    /// * `loop_body` - ループ本体のステートメント配列
+    ///
+    /// # Returns
+    /// ループ内にContinueがあればtrue
+    pub(crate) fn has_continue_in_loop_body(loop_body: &[serde_json::Value]) -> bool {
+        loop_body.iter().any(|stmt| {
+            if stmt["type"].as_str() == Some("If") {
+                let then_has = stmt["then"]
+                    .as_array()
+                    .map(|body| {
+                        body.iter()
+                            .any(|s| s["type"].as_str() == Some("Continue"))
+                    })
+                    .unwrap_or(false);
+                let else_has = stmt["else"]
+                    .as_array()
+                    .map(|body| {
+                        body.iter()
+                            .any(|s| s["type"].as_str() == Some("Continue"))
+                    })
+                    .unwrap_or(false);
+                then_has || else_has
+            } else {
+                false
+            }
+        })
+    }
 }