phase29ao(p43): add coreloop composer v0 scaffold

docs/development/current/main/10-Now.md

@@ -3,7 +3,7 @@
 ## Current Focus
 
 - Phase: `docs/development/current/main/phases/phase-29ao/README.md`
-- Next: `docs/development/current/main/phases/phase-29ao/P43-CORELOOPCOMPOSER-V0-SCAFFOLD-INSTRUCTIONS.md`
+- Next: TBD (see `docs/development/current/main/phases/phase-29ao/README.md`)
 
 ## Gate (SSOT)
 

docs/development/current/main/30-Backlog.md

@@ -5,7 +5,7 @@ Scope: 「次にやる候補」を短く列挙するメモ。入口は `docs/dev
 
 ## Active
 
-- CorePlan migration: `docs/development/current/main/phases/phase-29ao/README.md`（Next: P43）
+- CorePlan migration: `docs/development/current/main/phases/phase-29ao/README.md`（Next: TBD）
 
 ## Near-Term Candidates
 

docs/development/current/main/design/coreplan-migration-roadmap-ssot.md

@@ -34,7 +34,7 @@ Related:
 ## 1.1 Current (active)
 
 - Active phase: `docs/development/current/main/phases/phase-29ao/README.md`
-- Next step: `docs/development/current/main/phases/phase-29ao/P43-CORELOOPCOMPOSER-V0-SCAFFOLD-INSTRUCTIONS.md`
+- Next step: TBD
 
 ## 2. すでに固めた SSOT（再発防止の土台）
 

docs/development/current/main/phases/phase-29ao/README.md

@@ -236,7 +236,11 @@ Gate（SSOT）:
 - 指示書: `docs/development/current/main/phases/phase-29ao/P42-STAGE3-CORELOOPCOMPOSER-V0-DESIGN-INSTRUCTIONS.md`
 - ねらい: Skeleton+Feature 合成による CoreLoopComposer v0 の境界を SSOT で固定（docs-first, 仕様不変）
 
+## P43: CoreLoopComposer v0 scaffold (unconnected) ✅
+
+- 指示書: `docs/development/current/main/phases/phase-29ao/P43-CORELOOPCOMPOSER-V0-SCAFFOLD-INSTRUCTIONS.md`
+- ねらい: CoreLoopComposer v0 の足場を追加し、合成入口の SSOT を先に固定（未接続, 仕様不変）
+
 ## Next（planned）
 
-- Next: P43（CoreLoopComposer v0 scaffold）
-- 指示書: `docs/development/current/main/phases/phase-29ao/P43-CORELOOPCOMPOSER-V0-SCAFFOLD-INSTRUCTIONS.md`
+- Next: TBD

src/mir/builder/control_flow/plan/composer/coreloop_v0.rs

@@ -0,0 +1,78 @@
+//! Phase 29ao P43: CoreLoopComposer v0 scaffold (unconnected).
+
+use crate::mir::builder::control_flow::plan::facts::skeleton_facts::SkeletonKind;
+use crate::mir::builder::control_flow::plan::normalize::CanonicalLoopFacts;
+use crate::mir::builder::control_flow::plan::CorePlan;
+
+#[allow(dead_code)]
+pub(in crate::mir::builder) fn try_compose_core_loop_v0(
+    facts: &CanonicalLoopFacts,
+) -> Result<Option<CorePlan>, String> {
+    if !matches!(facts.skeleton_kind, SkeletonKind::Loop) {
+        return Ok(None);
+    }
+    if facts.value_join_needed {
+        return Ok(None);
+    }
+    Ok(None)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::try_compose_core_loop_v0;
+    use crate::mir::builder::control_flow::plan::facts::feature_facts::{
+        LoopFeatureFacts, ValueJoinFacts,
+    };
+    use crate::mir::builder::control_flow::plan::facts::loop_facts::LoopFacts;
+    use crate::mir::builder::control_flow::plan::facts::scan_shapes::{
+        ConditionShape, StepShape,
+    };
+    use crate::mir::builder::control_flow::plan::facts::skeleton_facts::{
+        SkeletonFacts, SkeletonKind,
+    };
+    use crate::mir::builder::control_flow::plan::normalize::canonicalize_loop_facts;
+
+    fn base_facts(
+        skeleton_kind: SkeletonKind,
+        features: LoopFeatureFacts,
+    ) -> LoopFacts {
+        LoopFacts {
+            condition_shape: ConditionShape::Unknown,
+            step_shape: StepShape::Unknown,
+            skeleton: SkeletonFacts {
+                kind: skeleton_kind,
+            },
+            features,
+            scan_with_init: None,
+            split_scan: None,
+            pattern1_simplewhile: None,
+            pattern3_ifphi: None,
+            pattern4_continue: None,
+            pattern5_infinite_early_exit: None,
+            pattern8_bool_predicate_scan: None,
+            pattern9_accum_const_loop: None,
+            pattern2_break: None,
+            pattern2_loopbodylocal: None,
+        }
+    }
+
+    #[test]
+    fn coreloop_v0_returns_none_for_non_loop_skeleton() {
+        let facts = base_facts(SkeletonKind::If2, LoopFeatureFacts::default());
+        let canonical = canonicalize_loop_facts(facts);
+        let composed = try_compose_core_loop_v0(&canonical).expect("Ok");
+        assert!(composed.is_none());
+    }
+
+    #[test]
+    fn coreloop_v0_returns_none_when_value_join_needed() {
+        let features = LoopFeatureFacts {
+            value_join: Some(ValueJoinFacts { needed: true }),
+            ..LoopFeatureFacts::default()
+        };
+        let facts = base_facts(SkeletonKind::Loop, features);
+        let canonical = canonicalize_loop_facts(facts);
+        let composed = try_compose_core_loop_v0(&canonical).expect("Ok");
+        assert!(composed.is_none());
+    }
+}

src/mir/builder/control_flow/plan/composer/mod.rs

@@ -1,5 +1,6 @@
 //! Phase 29ao P0: CorePlan composer scaffold (CanonicalLoopFacts -> CorePlan)
 
+pub(super) mod coreloop_v0;
 mod shadow_adopt;
 
 use super::{normalizer::PlanNormalizer, CorePlan, DomainPlan, Pattern1SimpleWhilePlan};