fix(joinir): Phase 170-B Break condition delegation to condition_to_joinir

Remove hardcoded break condition (i >= 2) from loop_with_break_minimal.rs.
Now delegates to condition_to_joinir for dynamic break condition lowering.

Changes:
- Add extract_break_condition() to ast_feature_extractor.rs
- Pattern2 lowerer extracts break condition AST and passes to lowerer
- loop_with_break_minimal.rs uses BoolExprLowerer instead of hardcoded values
- Add TrimTest.main/0 to JoinIR routing whitelist

Box Theory compliance:
- Single responsibility: Pattern2 handles structure, condition_to_joinir handles lowering
- Zero hardcoding: All break conditions now dynamic

Verified:
- test_loop_return.hako (i >= 2) → RC: 2 ✅
- test_trim_loop.hako (i >= 3) → RC: 3 ✅

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

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

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

@@ -76,6 +76,7 @@ impl MirBuilder {
             "TrimTest.trim/1" => true,
             "Main.trim/1" => true,  // Phase 171-fix: Main box variant
             "Main.trim_string_simple/1" => true,  // Phase 33-13: Simple trim variant
+            "TrimTest.main/0" => true,  // Phase 170: TrimTest.main for loop pattern test
             _ => false,
         };