refactor(joinir): Phase 229 - Remove redundant ConditionAlias

Replace static alias mapping with dynamic condition variable resolution using:
- promoted_loopbodylocals as source of truth
- Naming conventions: is_<var> or is_<var>_match
- Pattern-aware inference during lowering

Benefits:
- Simpler data structure (6 fields → 5)
- Single source of truth
- Self-documenting with explicit naming conventions
- Fewer maintenance points

Net: -25 lines (60 additions, 85 deletions)
Tests: 877/884 PASS (no regressions)

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

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

src/mir/loop_pattern_detection/loop_body_carrier_promoter.rs

@@ -83,11 +83,9 @@ impl TrimPatternInfo {
         // Phase 171-C-5: Attach TrimLoopHelper for pattern-specific lowering logic
         carrier_info.trim_helper = Some(TrimLoopHelper::from_pattern_info(self));
 
-        // Phase 224-D: Record condition alias for promoted variable
-        carrier_info.condition_aliases.push(crate::mir::join_ir::lowering::carrier_info::ConditionAlias {
-            old_name: self.var_name.clone(),
-            carrier_name: self.carrier_name.clone(),
-        });
+        // Phase 229: Record promoted variable (no need for condition_aliases)
+        // Dynamic resolution uses promoted_loopbodylocals + naming convention
+        carrier_info.promoted_loopbodylocals.push(self.var_name.clone());
 
         carrier_info
     }

src/mir/loop_pattern_detection/loop_body_digitpos_promoter.rs

@@ -199,18 +199,16 @@ impl DigitPosPromoter {
                     vec![promoted_carrier],
                 );
 
-                // Phase 224-D: Record condition alias for promoted variable
-                carrier_info.condition_aliases.push(crate::mir::join_ir::lowering::carrier_info::ConditionAlias {
-                    old_name: var_in_cond.clone(),
-                    carrier_name: carrier_name.clone(),
-                });
+                // Phase 229: Record promoted variable (no need for condition_aliases)
+                // Dynamic resolution uses promoted_loopbodylocals + naming convention
+                carrier_info.promoted_loopbodylocals.push(var_in_cond.clone());
 
                 eprintln!(
                     "[digitpos_promoter] A-4 DigitPos pattern promoted: {} → {}",
                     var_in_cond, carrier_name
                 );
                 eprintln!(
-                    "[digitpos_promoter] Phase 224-D: Added condition alias '{}' → '{}'",
+                    "[digitpos_promoter] Phase 229: Recorded promoted variable '{}' (carrier: '{}')",
                     var_in_cond, carrier_name
                 );