feat(joinir): Phase 183 LoopBodyLocal role separation + test fixes

Phase 183 Implementation:
- Added is_var_used_in_condition() helper for AST variable detection
- Implemented LoopBodyLocal filtering in TrimLoopLowerer
- Created 4 test files for P1/P2 patterns
- Added 5 unit tests for variable detection

Test Fixes:
- Fixed test_is_outer_scope_variable_pinned (BasicBlockId import)
- Fixed test_pattern2_accepts_loop_param_only (literal node usage)

Refactoring:
- Unified pattern detection documentation
- Consolidated CarrierInfo initialization
- Documented LoopScopeShape construction paths

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

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

src/tests/identical_exec_instance.rs

@@ -1,9 +1,9 @@
 #[cfg(all(test, not(feature = "jit-direct-only")))]
 mod tests {
     use std::collections::HashMap;
-    use std::sync::{Arc, RwLock};
+    
 
-    use crate::backend::VM;
+    
     use crate::box_factory::RuntimeError;
     use crate::box_trait::NyashBox;
     use crate::mir::{