refactor(joinir): Phase 242-EX-A - Delete legacy Pattern3 lowerer

Remove hardcoded Pattern3 PoC implementation (loop_with_if_phi_minimal.rs)
and enhance if-sum mode to handle complex conditions like `i % 2 == 1`.

Key changes:
- condition_pattern.rs: Accept BinaryOp in comparison operands (+58 lines)
- loop_with_if_phi_if_sum.rs: Dynamic complex condition lowering (+147 lines)
- pattern3_with_if_phi.rs: Remove lower_pattern3_legacy() (-130 lines)
- loop_with_if_phi_minimal.rs: Delete entire file (-437 lines)
- loop_patterns/with_if_phi.rs: Update stub (-45 lines)
- mod.rs: Remove module reference (-4 lines)

Net reduction: -664 lines of hardcoded PoC code

Test results: 909/909 PASS (legacy mode completely removed)

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

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

src/mir/join_ir/lowering/mod.rs

@@ -62,8 +62,8 @@ pub mod loop_to_join;
 pub(crate) mod loop_view_builder; // Phase 33-23: Loop lowering dispatch
 pub mod loop_with_break_minimal; // Phase 188-Impl-2: Pattern 2 minimal lowerer
 pub mod loop_with_continue_minimal; // Phase 195: Pattern 4 minimal lowerer
-pub mod loop_with_if_phi_minimal; // Phase 188-Impl-3: Pattern 3 minimal lowerer
-pub mod loop_with_if_phi_if_sum; // Phase 213: Pattern 3 AST-based if-sum lowerer
+// Phase 242-EX-A: loop_with_if_phi_minimal removed - replaced by loop_with_if_phi_if_sum
+pub mod loop_with_if_phi_if_sum; // Phase 213: Pattern 3 AST-based if-sum lowerer (Phase 242-EX-A: supports complex conditions)
 pub mod simple_while_minimal; // Phase 188-Impl-1: Pattern 1 minimal lowerer
 pub mod min_loop;
 pub mod skip_ws;