refactor(joinir): Phase 223 cleanup - impl consolidation & comment cleanup

Improves code organization and readability after Phase 223-3 implementation.

## Task R-1: impl Block Consolidation

**loop_body_cond_promoter.rs**:
- Merged 2 separate impl blocks into single unified impl
- Added section headers for better organization:
  - Public API (extract_continue_condition, try_promote_for_condition)
  - Private Helpers (contains_continue)
- Improved logical flow and discoverability

## Task R-2: Phase Comment Cleanup

**pattern4_with_continue.rs**:
- Simplified Phase 223-3 comments (removed redundant phase numbers)
- Added concise section header explaining LoopBodyLocal promotion
- Clarified inline comments for better understanding
- Maintained implementation intent while reducing noise

## Impact

- No functional changes
- All tests PASS (5 cond_promoter tests, 8 pattern4 tests)
- Better code organization for future maintenance
- Cleaner git history for Phase 223

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

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

src/mir/loop_pattern_detection/loop_body_cond_promoter.rs

@@ -85,6 +85,10 @@ pub enum ConditionPromotionResult {
 pub struct LoopBodyCondPromoter;
 
 impl LoopBodyCondPromoter {
+    // ========================================================================
+    // Public API
+    // ========================================================================
+
     /// Extract continue condition from loop body
     ///
     /// Finds the first if statement with continue in then-branch and returns its condition.
@@ -123,33 +127,6 @@ impl LoopBodyCondPromoter {
         None
     }
 
-    /// Check if statements contain a continue statement
-    fn contains_continue(stmts: &[ASTNode]) -> bool {
-        for stmt in stmts {
-            match stmt {
-                ASTNode::Continue { .. } => return true,
-                ASTNode::If {
-                    then_body,
-                    else_body,
-                    ..
-                } => {
-                    if Self::contains_continue(then_body) {
-                        return true;
-                    }
-                    if let Some(else_stmts) = else_body {
-                        if Self::contains_continue(else_stmts) {
-                            return true;
-                        }
-                    }
-                }
-                _ => {}
-            }
-        }
-        false
-    }
-}
-
-impl LoopBodyCondPromoter {
     /// Try to promote LoopBodyLocal variables in conditions
     ///
     /// ## P0 Requirements (Category A-3)
@@ -223,6 +200,35 @@ impl LoopBodyCondPromoter {
             }
         }
     }
+
+    // ========================================================================
+    // Private Helpers
+    // ========================================================================
+
+    /// Check if statements contain a continue statement
+    fn contains_continue(stmts: &[ASTNode]) -> bool {
+        for stmt in stmts {
+            match stmt {
+                ASTNode::Continue { .. } => return true,
+                ASTNode::If {
+                    then_body,
+                    else_body,
+                    ..
+                } => {
+                    if Self::contains_continue(then_body) {
+                        return true;
+                    }
+                    if let Some(else_stmts) = else_body {
+                        if Self::contains_continue(else_stmts) {
+                            return true;
+                        }
+                    }
+                }
+                _ => {}
+            }
+        }
+        false
+    }
 }
 
 #[cfg(test)]