feat(joinir): Phase 213-2 Step 2-2 & 2-3 Data structure extensions

Extended PatternPipelineContext and CarrierUpdateInfo for Pattern 3 AST-based generalization.

Changes:
1. PatternPipelineContext:
   - Added loop_condition: Option<ASTNode>
   - Added loop_body: Option<Vec<ASTNode>>
   - Added loop_update_summary: Option<LoopUpdateSummary>
   - Updated build_pattern_context() for Pattern 3

2. CarrierUpdateInfo:
   - Added then_expr: Option<ASTNode>
   - Added else_expr: Option<ASTNode>
   - Updated analyze_loop_updates() with None defaults

Status: Phase 213-2 Steps 2-2 & 2-3 complete
Next: Create Pattern3IfAnalyzer to extract if statement and populate update summary

src/mir/join_ir/lowering/loop_scope_shape/case_a_lowering_shape.rs

@@ -103,6 +103,7 @@ impl CaseALoweringShape {
     /// * `features` - LoopFeatures (structure-based, name-agnostic)
     /// * `carrier_count` - Number of carrier variables from LoopScopeShape
     /// * `has_progress_carrier` - Whether progress carrier exists
+    #[allow(dead_code)]
     pub fn detect_from_features(
         features: &crate::mir::loop_pattern_detection::LoopFeatures,
         carrier_count: usize,
@@ -165,6 +166,7 @@ impl CaseALoweringShape {
     ///
     /// # Returns
     /// More precise CaseALoweringShape classification
+    #[allow(dead_code)]
     pub fn detect_with_carrier_name(
         features: &crate::mir::loop_pattern_detection::LoopFeatures,
         carrier_count: usize,
@@ -271,6 +273,7 @@ impl CaseALoweringShape {
     ///
     /// ArrayAccumulation パターンは通常：
     /// - より意味のある名前 ('result', 'items', 'defs' など)
+    #[allow(dead_code)]
     fn is_typical_index_name(name: &str) -> bool {
         matches!(
             name,
@@ -285,6 +288,7 @@ impl CaseALoweringShape {
         since = "Phase 170-A",
         note = "Use detect_from_features() with LoopFeatures instead"
     )]
+    #[allow(dead_code)]
     pub fn detect(scope: &super::shape::LoopScopeShape) -> Self {
         // Construct minimal LoopFeatures from LoopScopeShape
         // Note: This loses some information (has_break, has_continue not available)
@@ -313,6 +317,7 @@ impl CaseALoweringShape {
     }
 
     /// Is this a recognized lowering shape?
+    #[allow(dead_code)]
     pub fn is_recognized(&self) -> bool {
         !matches!(self, CaseALoweringShape::NotCaseA | CaseALoweringShape::Generic)
     }

src/mir/join_ir/lowering/loop_scope_shape/shape.rs

@@ -73,6 +73,7 @@ impl LoopVarClass {
 #[derive(Debug, Clone)]
 pub(crate) struct LoopScopeShape {
     pub header: BasicBlockId,
+    #[allow(dead_code)]
     pub body: BasicBlockId,
     pub latch: BasicBlockId,
     pub exit: BasicBlockId,

src/mir/join_ir/lowering/loop_scope_shape/structural.rs

@@ -81,11 +81,13 @@ impl LoopStructuralAnalysis {
     /// - 出口グループ数の確認
     /// - 非局所 exit の有無確認
     /// - 出口先ブロックの取得
+    #[allow(dead_code)]
     pub fn exit_analysis(&self) -> &ExitAnalysis {
         &self.exit_analysis
     }
 
     /// progress_carrier の有無
+    #[allow(dead_code)]
     pub fn has_progress_carrier(&self) -> bool {
         self.has_progress_carrier
     }