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/builder/control_flow/joinir/patterns/pattern2_with_break.rs

@@ -308,6 +308,9 @@ impl MirBuilder {
                             promoted_var, carrier_name
                         );
 
+                        // Phase 224: Record promoted variable before merging
+                        carrier_info.promoted_loopbodylocals.push(promoted_var.clone());
+
                         // Merge promoted carrier into existing CarrierInfo
                         carrier_info.merge_from(&promoted_carrier);
 
@@ -316,6 +319,10 @@ impl MirBuilder {
                             carrier_name,
                             carrier_info.carrier_count()
                         );
+                        eprintln!(
+                            "[pattern2/cond_promoter] Phase 224: Recorded promoted variable '{}' in carrier_info.promoted_loopbodylocals",
+                            promoted_var
+                        );
 
                         // Check if this is a safe Trim pattern
                         if let Some(helper) = carrier_info.trim_helper() {

src/mir/builder/control_flow/joinir/patterns/pattern4_carrier_analyzer.rs

@@ -72,6 +72,7 @@ impl Pattern4CarrierAnalyzer {
             loop_var_id: all_carriers.loop_var_id,
             carriers: updated_carriers,
             trim_helper: all_carriers.trim_helper.clone(),
+            promoted_loopbodylocals: all_carriers.promoted_loopbodylocals.clone(), // Phase 224
         })
     }
 
@@ -287,6 +288,7 @@ mod tests {
                 },
             ],
             trim_helper: None,
+            promoted_loopbodylocals: Vec::new(), // Phase 224
         };
 
         // Analyze carriers

src/mir/builder/control_flow/joinir/patterns/pattern_pipeline.rs

@@ -404,6 +404,7 @@ mod tests {
                     },
                 ],
                 trim_helper: None,
+                promoted_loopbodylocals: Vec::new(), // Phase 224
             },
             loop_scope: LoopScopeShapeBuilder::empty_body_locals(
                 BasicBlockId(0),
@@ -442,6 +443,7 @@ mod tests {
                     carrier_name: "is_whitespace".to_string(),
                     whitespace_chars: vec![" ".to_string(), "\t".to_string()],
                 }),
+                promoted_loopbodylocals: Vec::new(), // Phase 224
             },
             loop_scope: LoopScopeShapeBuilder::empty_body_locals(
                 BasicBlockId(0),

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!(