feat(joinir): Phase 224-cont - Promoted variable tracking for lowerer

- Add promoted_loopbodylocals field to CarrierInfo
- Record promoted variables in Pattern2 promotion handler
- Filter promoted variables in lowerer LoopBodyLocal check
- digit_pos → is_digit_pos promotion now continues to lowering

Closes Phase 224 lowerer integration gap.

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

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

src/mir/join_ir/lowering/carrier_info.rs

@@ -46,6 +46,12 @@ pub struct CarrierInfo {
     pub carriers: Vec<CarrierVar>,
     /// Phase 171-C-5: Trim pattern helper (if this CarrierInfo was created from Trim promotion)
     pub trim_helper: Option<crate::mir::loop_pattern_detection::trim_loop_helper::TrimLoopHelper>,
+    /// Phase 224: Promoted LoopBodyLocal variables (e.g., "digit_pos" promoted to "is_digit_pos")
+    ///
+    /// These variables were originally LoopBodyLocal but have been promoted to carriers
+    /// during condition promotion (e.g., DigitPosPromoter). The lowerer should skip
+    /// LoopBodyLocal checks for these variables.
+    pub promoted_loopbodylocals: Vec<String>,
 }
 
 impl CarrierInfo {
@@ -106,6 +112,7 @@ impl CarrierInfo {
             loop_var_id,
             carriers,
             trim_helper: None, // Phase 171-C-5: No Trim pattern by default
+            promoted_loopbodylocals: Vec::new(), // Phase 224: No promoted variables by default
         })
     }
 
@@ -163,6 +170,7 @@ impl CarrierInfo {
             loop_var_id,
             carriers,
             trim_helper: None, // Phase 171-C-5: No Trim pattern by default
+            promoted_loopbodylocals: Vec::new(), // Phase 224: No promoted variables by default
         })
     }
 
@@ -189,6 +197,7 @@ impl CarrierInfo {
             loop_var_id,
             carriers,
             trim_helper: None, // Phase 171-C-5: No Trim pattern by default
+            promoted_loopbodylocals: Vec::new(), // Phase 224: No promoted variables by default
         }
     }
 
@@ -242,6 +251,13 @@ impl CarrierInfo {
         if other.trim_helper.is_some() {
             self.trim_helper = other.trim_helper.clone();
         }
+
+        // Phase 224: Merge promoted_loopbodylocals (deduplicate)
+        for promoted_var in &other.promoted_loopbodylocals {
+            if !self.promoted_loopbodylocals.contains(promoted_var) {
+                self.promoted_loopbodylocals.push(promoted_var.clone());
+            }
+        }
     }
 
     /// Phase 171-C-5: Get Trim pattern helper

src/mir/join_ir/lowering/loop_with_break_minimal.rs

@@ -154,8 +154,29 @@ pub(crate) fn lower_loop_with_break_minimal(
     );
 
     if loop_cond_scope.has_loop_body_local() {
+        // Phase 224: Filter out promoted variables from body-local check
+        // Variables that were promoted to carriers should not trigger the error
         let body_local_names = extract_body_local_names(&loop_cond_scope.vars);
-        return Err(format_unsupported_condition_error("pattern2", &body_local_names));
+        let unpromoted_locals: Vec<&String> = body_local_names
+            .iter()
+            .filter(|name| !carrier_info.promoted_loopbodylocals.contains(*name))
+            .copied()
+            .collect();
+
+        if !unpromoted_locals.is_empty() {
+            eprintln!(
+                "[joinir/pattern2] Phase 224: {} body-local variables after promotion filter: {:?}",
+                unpromoted_locals.len(),
+                unpromoted_locals
+            );
+            return Err(format_unsupported_condition_error("pattern2", &unpromoted_locals));
+        }
+
+        eprintln!(
+            "[joinir/pattern2] Phase 224: All {} body-local variables were promoted: {:?}",
+            body_local_names.len(),
+            body_local_names
+        );
     }
 
     eprintln!(