feat(joinir): Phase 228-8 - ConditionOnly carrier latch incoming support

- ExitMetaCollector includes ConditionOnly carriers in exit_bindings (for latch)
- ExitLineReconnector skips ConditionOnly in variable_map updates
- Pattern 2/3/4 pass carrier_info to ExitMetaCollector
- Resolves "has no latch incoming set" error

Role separation:
- Header PHI: entry + latch for both LoopState and ConditionOnly
- Exit PHI: LoopState only (ConditionOnly excluded)
- variable_map: LoopState only (ConditionOnly skipped)

🤖 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

@@ -546,8 +546,9 @@ impl MirBuilder {
         let exit_meta = &fragment_meta.exit_meta;
 
         // Phase 33-10: Collect exit bindings from ExitMeta using Box
+        // Phase 228-8: Pass carrier_info to include ConditionOnly carriers
         use crate::mir::builder::control_flow::joinir::merge::exit_line::ExitMetaCollector;
-        let exit_bindings = ExitMetaCollector::collect(self, &exit_meta, debug);
+        let exit_bindings = ExitMetaCollector::collect(self, &exit_meta, Some(&carrier_info), debug);
 
         // Phase 176-3: Build input mappings for all carriers
         // JoinIR main() params: [ValueId(0), ValueId(1), ValueId(2), ...] for (i, carrier1, carrier2, ...)

src/mir/builder/control_flow/joinir/patterns/pattern3_with_if_phi.rs

@@ -154,7 +154,8 @@ impl MirBuilder {
         }
 
         // Build exit bindings using ExitMetaCollector
-        let exit_bindings = ExitMetaCollector::collect(self, exit_meta, debug);
+        // Phase 228-8: Pass carrier_info to include ConditionOnly carriers
+        let exit_bindings = ExitMetaCollector::collect(self, exit_meta, Some(&ctx.carrier_info), debug);
 
         // Build boundary with carrier inputs
         use crate::mir::join_ir::lowering::JoinInlineBoundaryBuilder;
@@ -297,9 +298,11 @@ impl MirBuilder {
         // Phase 213: Use ExitMetaCollector for dynamic exit binding generation
         // Note: ExitMetaCollector internally validates that all exit carriers in ExitMeta
         // have corresponding variable_map entries. No additional validation needed here.
+        // Phase 228-8: Pass None for carrier_info (legacy path doesn't have ConditionOnly carriers)
         let exit_bindings = ExitMetaCollector::collect(
             self,
             exit_meta,
+            None, // Phase 228-8: No carrier_info in legacy path
             debug,
         );
 

src/mir/builder/control_flow/joinir/patterns/pattern4_with_continue.rs

@@ -330,10 +330,12 @@ impl MirBuilder {
 
         // Phase 179 Task 2: Use ExitMetaCollector for unified exit binding generation
         // Replaces manual loop (Phase 196 implementation) with modular Box approach
+        // Phase 228-8: Pass carrier_info to include ConditionOnly carriers
         use super::super::merge::exit_line::meta_collector::ExitMetaCollector;
         let exit_bindings = ExitMetaCollector::collect(
             self,
             &exit_meta,
+            Some(&carrier_info), // Phase 228-8: Include ConditionOnly carriers
             debug,
         );