feat(joinir): Phase 248 - Normalized JoinIR infrastructure

Major refactoring of JoinIR normalization pipeline:

Key changes:
- Structured→Normalized→MIR(direct) pipeline established
- ShapeGuard enhanced with Pattern2 loop validation
- dev_env.rs: New development fixtures and env control
- fixtures.rs: jsonparser_parse_number_real fixture
- normalized_bridge/direct.rs: Direct MIR generation from Normalized
- pattern2_step_schedule.rs: Extracted step scheduling logic

Files changed:
- normalized.rs: Enhanced NormalizedJoinModule with DevEnv support
- shape_guard.rs: Pattern2-specific validation (+300 lines)
- normalized_bridge.rs: Unified bridge with direct path
- loop_with_break_minimal.rs: Integrated step scheduling
- Deleted: step_schedule.rs (moved to pattern2_step_schedule.rs)

New files:
- param_guess.rs: Loop parameter inference
- pattern2_step_schedule.rs: Step scheduling for Pattern2
- phase43-norm-canon-p2-mid.md: Design doc

Tests: 937/937 PASS (+6 from baseline 931)

🤖 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

@@ -8,9 +8,11 @@ use crate::mir::join_ir::lowering::condition_env::{ConditionBinding, ConditionEn
 use crate::mir::join_ir::lowering::join_value_space::JoinValueSpace;
 use crate::mir::join_ir::lowering::loop_body_local_env::LoopBodyLocalEnv;
 use crate::mir::join_ir::lowering::loop_scope_shape::LoopScopeShape;
+use crate::mir::join_ir::lowering::loop_update_analyzer::UpdateExpr;
 use crate::mir::loop_pattern_detection::function_scope_capture::CapturedEnv;
 use crate::mir::loop_pattern_detection::error_messages;
 use crate::mir::ValueId;
+use std::collections::BTreeMap;
 
 fn log_pattern2(verbose: bool, tag: &str, message: impl AsRef<str>) {
     if verbose {
@@ -701,25 +703,19 @@ impl MirBuilder {
             verbose,
             "updates",
             format!(
-                "Phase 176-3: Analyzed {} carrier updates",
-                carrier_updates.len()
-            ),
-        );
+        "Phase 176-3: Analyzed {} carrier updates",
+        carrier_updates.len()
+    ),
+    );
 
         let original_carrier_count = inputs.carrier_info.carriers.len();
-        inputs.carrier_info.carriers.retain(|carrier| {
-            use crate::mir::join_ir::lowering::carrier_info::{CarrierInit, CarrierRole};
-            carrier_updates.contains_key(&carrier.name)
-                || carrier.role == CarrierRole::ConditionOnly
-                || carrier.init == CarrierInit::FromHost
-                || carrier.init == CarrierInit::LoopLocalZero
-        });
+        filter_carriers_for_updates(&mut inputs.carrier_info, &carrier_updates);
 
         log_pattern2(
             verbose,
             "updates",
             format!(
-                "Phase 176-4: Filtered carriers: {} → {} (kept only carriers with updates)",
+                "Phase 176-4: Filtered carriers: {} → {} (kept only carriers with updates/condition-only/loop-local-zero)",
                 original_carrier_count,
                 inputs.carrier_info.carriers.len()
             ),
@@ -858,6 +854,19 @@ impl MirBuilder {
     }
 }
 
+/// 更新を持たない FromHost キャリアを落とすヘルパー。
+fn filter_carriers_for_updates(
+    carrier_info: &mut CarrierInfo,
+    carrier_updates: &BTreeMap<String, UpdateExpr>,
+) {
+    use crate::mir::join_ir::lowering::carrier_info::{CarrierInit, CarrierRole};
+    carrier_info.carriers.retain(|carrier| {
+        carrier_updates.contains_key(&carrier.name)
+            || carrier.role == CarrierRole::ConditionOnly
+            || carrier.init == CarrierInit::LoopLocalZero
+    });
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;