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/runtime/plugin_host.rs

@@ -304,7 +304,6 @@ impl PluginHost {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::runtime::core_services::*;
 
     #[test]
     fn test_plugin_descriptor() {

src/runtime/tests.rs

@@ -5,7 +5,7 @@
 #[cfg(test)]
 mod tests {
     use super::super::{BoxFactoryRegistry, PluginConfig};
-    use crate::bid::{BidHandle, BoxTypeId};
+    
     use crate::box_trait::{NyashBox, StringBox};
     use crate::runtime::box_registry::BoxProvider;