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/loop_pattern_detection/function_scope_capture.rs

@@ -135,7 +135,8 @@ impl CapturedEnv {
 /// # Returns
 ///
 /// `CapturedEnv` containing all captured variables
-pub fn analyze_captured_vars(
+#[allow(dead_code)]
+pub(crate) fn analyze_captured_vars(
     fn_body: &[ASTNode],
     loop_ast: &ASTNode,
     scope: &LoopScopeShape,
@@ -264,7 +265,8 @@ pub fn analyze_captured_vars(
 /// # Returns
 ///
 /// `CapturedEnv` containing all captured variables
-pub fn analyze_captured_vars_v2(
+#[allow(dead_code)]
+pub(crate) fn analyze_captured_vars_v2(
     fn_body: &[ASTNode],
     loop_condition: &ASTNode,
     loop_body: &[ASTNode],
@@ -379,6 +381,7 @@ pub fn analyze_captured_vars_v2(
 /// Find the index of a loop statement in the function body
 ///
 /// Returns Some(index) if found, None otherwise.
+#[allow(dead_code)]
 fn find_stmt_index(fn_body: &[ASTNode], loop_ast: &ASTNode) -> Option<usize> {
     // Compare by pointer address (same AST node instance)
     fn_body.iter().position(|stmt| {
@@ -545,6 +548,7 @@ fn is_reassigned_in_fn(fn_body: &[ASTNode], name: &str) -> bool {
 /// Check if variable is referenced in loop condition or body
 ///
 /// Returns true if the variable name appears anywhere in the loop AST.
+#[allow(dead_code)]
 fn is_used_in_loop(loop_ast: &ASTNode, name: &str) -> bool {
     fn check_usage(node: &ASTNode, name: &str) -> bool {
         match node {

src/mir/loop_pattern_detection/loop_body_carrier_promoter.rs

@@ -27,6 +27,7 @@ use crate::mir::loop_pattern_detection::loop_condition_scope::LoopConditionScope
 /// 昇格リクエスト
 pub struct PromotionRequest<'a> {
     /// ループのスコープ情報
+    #[allow(dead_code)]
     pub(crate) scope: &'a LoopScopeShape,
     /// 条件変数のスコープ分類
     pub cond_scope: &'a LoopConditionScope,