refactor(joinir): Phase 244 - ConditionLoweringBox trait unification

Unify condition lowering logic across Pattern 2/4 with trait-based API.

New infrastructure:
- condition_lowering_box.rs: ConditionLoweringBox trait + ConditionContext (293 lines)
- ExprLowerer implements ConditionLoweringBox trait (+51 lines)

Pattern migrations:
- Pattern 2 (loop_with_break_minimal.rs): Use trait API
- Pattern 4 (loop_with_continue_minimal.rs): Use trait API

Benefits:
- Unified condition lowering interface
- Extensible for future lowering strategies
- Clean API boundary between patterns and lowering logic
- Zero code duplication

Test results: 911/911 PASS (+2 new tests)

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

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

docs/development/current/main/phase202-summary.md

@@ -270,3 +270,5 @@ ae741d97 feat(joinir): Phase 202-C Pattern 4 uses JoinValueSpace, unify dual cou
 Phase 202 achieved complete architectural consistency across all JoinIR loop patterns by migrating Pattern 1, 3, and 4 to the unified JoinValueSpace system. This eliminates all ValueId collision risks, simplifies maintenance, and establishes a solid foundation for future JoinIR enhancements.
 
 **Key Achievement**: 4/4 patterns (100%) now use JoinValueSpace, with 0 manual counter systems remaining in the codebase.
+Status: Active  
+Scope: Join Value Space 適用サマリー（JoinIR v2）