refactor(joinir): Phase 92 P1 - 箱化モジュール化・レガシー削除

P1-1: ConditionalStep lowering を1箱に隔離
- 新規作成: src/mir/join_ir/lowering/common/conditional_step_emitter.rs
  - emit_conditional_step_update() を carrier_update_emitter.rs から移動
  - Fail-Fast 不変条件チェック追加（then_delta != else_delta）
  - 副作用を減らしたクリーンなインターフェース
  - 包括的なテストスイート（3テスト）

P1-0: 境界SSOTの固定
- routing.rs: skeleton 設定をrouting層から削除
- pattern2_with_break.rs: skeleton 取得をlower()内部に閉じ込め
  - parity_checker から skeleton を直接取得
  - skeleton の使用を Pattern2 のみに限定

P1-2: escape recognizer をSSOTに戻す
- escape_pattern_recognizer.rs: 未使用フィールド削除
  - quote_char, escape_char 削除（使われていない）
  - 責務を cond/delta 抽出のみに限定
- pattern_recognizer.rs: デフォルト値を使用

P1-3: E2Eテスト作成（実行は後回し）
- apps/tests/test_pattern5b_escape_minimal.hako 作成
  - body-local 変数対応後に検証予定

テスト結果:
- conditional_step_emitter tests: 3 passed
- Pattern2 tests: 18 passed
- Regression: 0 failures

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

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

src/mir/builder/control_flow/joinir/patterns/escape_pattern_recognizer.rs

@@ -12,17 +12,20 @@
 use crate::ast::{ASTNode, BinaryOperator, LiteralValue};
 
 /// Information about a detected escape skip pattern
+///
+/// Phase 92 P1-2: Responsibility limited to cond/delta extraction only.
+/// Body-local variable handling (`ch`) should be done by canonicalizer/caller.
 #[derive(Debug, Clone)]
 pub struct EscapeSkipPatternInfo {
     pub counter_name: String,
     pub normal_delta: i64,
     pub escape_delta: i64,
-    pub quote_char: char,
-    pub escape_char: char,
-    pub body_stmts: Vec<ASTNode>,
     /// Phase 92 P0-3: The condition expression for conditional increment
     /// e.g., `ch == '\\'` for escape sequence handling
     pub escape_cond: Box<ASTNode>,
+    /// Body statements before break check (for reference)
+    /// Note: Caller should handle body-local variable extraction (e.g., `ch`)
+    pub body_stmts: Vec<ASTNode>,
 }
 
 /// Detect escape sequence handling pattern in loop body
@@ -71,10 +74,8 @@ pub fn detect_escape_skip_pattern(body: &[ASTNode]) -> Option<EscapeSkipPatternI
         counter_name,
         normal_delta,
         escape_delta,
-        quote_char: '"',  // Default for JSON/CSV (Phase 91 MVP)
-        escape_char: '\\',  // Default for JSON/CSV (Phase 91 MVP)
-        body_stmts,
         escape_cond,  // Phase 92 P0-3: Condition for JoinIR Select
+        body_stmts,
     })
 }
 

src/mir/builder/control_flow/joinir/patterns/pattern2_with_break.rs

@@ -717,18 +717,34 @@ pub(crate) fn can_lower(builder: &MirBuilder, ctx: &super::router::LoopPatternCo
 ///
 /// Wrapper around cf_loop_pattern2_with_break to match router signature
 /// Phase 200-C: Pass fn_body to cf_loop_pattern2_with_break
-/// Phase 92 P0-3: Pass skeleton for ConditionalStep support
+/// Phase 92 P1-0: Retrieve skeleton internally for ConditionalStep support
 pub(crate) fn lower(
     builder: &mut MirBuilder,
     ctx: &super::router::LoopPatternContext,
 ) -> Result<Option<ValueId>, String> {
+    // Phase 92 P1-0: Retrieve skeleton from parity checker if dev mode enabled
+    // verify_router_parity is a method on MirBuilder, accessible directly
+    let skeleton = if crate::config::env::joinir_dev_enabled() {
+        let (_parity_result, skeleton_opt) = builder.verify_router_parity(
+            ctx.condition,
+            ctx.body,
+            ctx.func_name,
+            ctx,
+        );
+        // Note: parity check errors are already logged by verify_router_parity
+        // We only need the skeleton for ConditionalStep support
+        skeleton_opt
+    } else {
+        None
+    };
+
     builder.cf_loop_pattern2_with_break_impl(
         ctx.condition,
         ctx.body,
         ctx.func_name,
         ctx.debug,
         ctx.fn_body,
-        ctx.skeleton,  // Phase 92 P0-3: Pass skeleton for ConditionalStep
+        skeleton.as_ref(),  // Phase 92 P1-0: Pass skeleton reference
     )
 }
 

src/mir/builder/control_flow/joinir/routing.rs

@@ -304,19 +304,10 @@ impl MirBuilder {
         };
 
         // Phase 137-4: Router parity verification (after ctx is created)
-        // Phase 92 P0-2: Get skeleton from canonicalizer for Option A
-        let skeleton_holder: Option<crate::mir::loop_canonicalizer::LoopSkeleton>;
+        // Phase 92 P1-0: Skeleton setting removed - patterns retrieve skeleton internally if needed
         if crate::config::env::joinir_dev_enabled() {
-            let (result, skeleton_opt) = self.verify_router_parity(condition, body, func_name, &ctx);
+            let (result, _skeleton_opt) = self.verify_router_parity(condition, body, func_name, &ctx);
             result?;
-            skeleton_holder = skeleton_opt;
-            if skeleton_holder.is_some() {
-                // Phase 92 P0-2: Set skeleton reference in context (must use holder lifetime)
-                // Note: This is safe because skeleton_holder lives for the entire scope
-                ctx.skeleton = skeleton_holder.as_ref();
-            }
-        } else {
-            skeleton_holder = None;
         }
 
         if let Some(result) = route_loop_pattern(self, &ctx)? {