refactor(plan): Phase 273 P3+ - Legacy code removal

Phase 273 P3+ 完成: レガシーコード削除 + 未使用 import 整理

Removed Legacy Items:
1. emit_scan_with_init_edgecfg() - Pattern6 固有の emission 関数
   - File deleted: src/mir/builder/emission/loop_scan_with_init.rs (~144 lines)
   - Replaced by: generalized Frag API (Phase 273 P2)

2. CoreCarrierInfo struct - Legacy carrier representation
   - Removed from: src/mir/builder/control_flow/plan/mod.rs (~15 lines)
   - Replaced by: CorePhiInfo (generalized PHI representation)

3. verify_carrier() function - CoreCarrierInfo validator
   - Removed from: src/mir/builder/control_flow/plan/verifier.rs (~15 lines)
   - Replaced by: generalized PHI verification (V7-V9)

Code Cleanup:
- cargo fix applied: unused imports removed (~30 files)
- Verifier invariants updated: V1→V2-V9 (carrier→PHI model)
- Module declaration cleanup in emission/mod.rs

Impact:
- Total lines removed: ~174 lines (net reduction)
- Pattern-agnostic architecture strengthened
- All legacy Pattern6 references eliminated

Tests:
- ✅ VM tests PASS (phase254/256/258)
- ✅ LLVM tests PASS (phase256/258)

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

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

src/mir/builder/control_flow/edgecfg/api/compose.rs

@@ -13,7 +13,6 @@ use std::collections::BTreeMap;
 use crate::mir::basic_block::{BasicBlockId, EdgeArgs};
 use crate::mir::control_form::LoopId;
 use crate::mir::value_id::ValueId;
-use crate::mir::join_ir::lowering::inline_boundary::JumpArgsLayout;
 use super::frag::Frag;
 use super::exit_kind::ExitKind;
 use super::edge_stub::EdgeStub;  // Phase 265 P2: wires/exits 分離で必要

src/mir/builder/control_flow/edgecfg/api/mod.rs

@@ -34,7 +34,7 @@ pub(crate) use compose::{seq, if_, loop_, cleanup};
 
 // 検証関数
 pub use verify::verify_frag_invariants;
-pub use verify::verify_frag_invariants_strict; // Phase 266: strict 版追加
+ // Phase 266: strict 版追加
 
 // Phase 267 P0: wires + branches → MIR terminator 変換
-pub use emit::{emit_wires, emit_frag};
+pub use emit::emit_frag;

src/mir/builder/control_flow/edgecfg/mod.rs

@@ -6,7 +6,5 @@
 pub mod api;
 
 // 公開型（安定）
-pub use api::{ExitKind, EdgeStub, Frag, verify_frag_invariants};
 
 // 合成関数（Phase 264: crate内のみ公開）
-pub(crate) use api::{seq, if_, loop_, cleanup};

src/mir/builder/control_flow/joinir/merge/instruction_rewriter.rs

@@ -18,8 +18,7 @@ use crate::mir::builder::joinir_id_remapper::JoinIrIdRemapper;
 use crate::mir::join_ir::lowering::error_tags;
 use crate::mir::join_ir::lowering::inline_boundary::JoinInlineBoundary;
 // Phase 256 P1.7: Removed join_func_name import - no longer needed
-use crate::mir::types::ConstValue;
-use crate::mir::{BasicBlock, BasicBlockId, MirFunction, MirInstruction, MirModule, MirType, ValueId};
+use crate::mir::{BasicBlock, BasicBlockId, MirInstruction, MirModule, ValueId};
 use std::collections::BTreeMap; // Phase 222.5-E: HashMap → BTreeMap for determinism
 use std::collections::BTreeSet;
 

src/mir/builder/control_flow/joinir/merge/rewriter/mod.rs

@@ -39,5 +39,5 @@ pub(super) mod terminator; // Phase 260 P0.1 Step 5: Terminator remapping extrac
 pub(super) mod type_propagation; // Phase 260 P0.1 Step 4: Type propagation extracted ✅
 
 // Re-export public API
-pub(super) use helpers::is_skippable_continuation; // Phase 260 P0.1 Step 3: From helpers ✅
+ // Phase 260 P0.1 Step 3: From helpers ✅
 pub(super) use super::instruction_rewriter::merge_and_rewrite; // Still in parent (TODO: extract)

src/mir/builder/control_flow/joinir/patterns/pattern2_lowering_orchestrator.rs

@@ -36,7 +36,6 @@ use super::pattern2_steps::gather_facts_step_box::GatherFactsStepBox;
 use super::pattern2_steps::merge_step_box::MergeStepBox;
 use super::pattern2_steps::normalize_body_step_box::NormalizeBodyStepBox;
 use super::pattern2_steps::post_loop_early_return_step_box::PostLoopEarlyReturnStepBox;
-use super::pattern2_steps::promote_step_box::PromoteStepBox;
 
 pub(crate) struct Pattern2LoweringOrchestrator;
 

src/mir/builder/control_flow/joinir/patterns/pattern2_steps/emit_joinir_step_box.rs

@@ -4,7 +4,6 @@
 
 use crate::ast::ASTNode;
 use crate::mir::builder::MirBuilder;
-use crate::mir::ValueId;
 
 use super::super::pattern2_inputs_facts_box::{Pattern2DebugLog, Pattern2Inputs};
 use crate::mir::join_ir::lowering::inline_boundary::JoinInlineBoundary;

src/mir/builder/control_flow/joinir/patterns/pattern2_steps/promote_step_box.rs

@@ -10,7 +10,7 @@
 use crate::ast::ASTNode;
 use crate::mir::builder::MirBuilder;
 
-use super::super::pattern2::api::{try_promote, PromoteDecision, PromoteStepResult};
+use super::super::pattern2::api::{try_promote, PromoteDecision};
 use super::super::pattern2_inputs_facts_box::Pattern2Inputs;
 
 pub(crate) struct PromoteStepBox;

src/mir/builder/control_flow/joinir/patterns/pattern6_scan_with_init.rs

@@ -33,11 +33,8 @@
 //! - MethodCall allowed_in_condition() = false, but allowed_in_init() = true
 //! - Need to hoist MethodCall to init phase
 
-use super::super::trace;
-use super::common::var; // Phase 255 P2: Use shared var() helper
-use crate::ast::{ASTNode, BinaryOperator, LiteralValue};
-use crate::mir::builder::MirBuilder;
-use crate::mir::ValueId;
+ // Phase 255 P2: Use shared var() helper
+use crate::ast::ASTNode;
 
 // Phase 273 P1: Import DomainPlan types (Plan renamed to DomainPlan)
 use crate::mir::builder::control_flow::plan::{DomainPlan, ScanDirection as PlanScanDirection, ScanWithInitPlan};

src/mir/builder/control_flow/joinir/patterns/pattern8_scan_bool_predicate.rs

@@ -34,7 +34,6 @@
 //! - Pattern 8: Returns boolean (true/false)
 
 use super::super::trace;
-use super::common::var;
 use crate::ast::{ASTNode, BinaryOperator, LiteralValue, UnaryOperator};
 use crate::mir::builder::MirBuilder;
 use crate::mir::ValueId;

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

@@ -192,21 +192,7 @@ pub(in crate::mir::builder) struct CoreLoopPlan {
     pub final_values: Vec<(String, ValueId)>,
 }
 
-/// Phase 273 P1: Loop carrier (PHI variable)
-#[derive(Debug, Clone)]
-pub(in crate::mir::builder) struct CoreCarrierInfo {
-    /// Variable name (for variable_map update)
-    pub name: String,
-
-    /// Initial value (from preheader)
-    pub init_value: ValueId,
-
-    /// Step value (from step block, back-edge)
-    pub step_value: ValueId,
-
-    /// PHI destination (loop variable inside loop)
-    pub phi_dst: ValueId,
-}
+// Phase 273 P3: CoreCarrierInfo removed (replaced by CorePhiInfo)
 
 /// Phase 273 P1: Conditional plan
 #[derive(Debug, Clone)]

src/mir/builder/control_flow/plan/normalizer.rs

@@ -12,7 +12,7 @@
 //! Lowerer processes CorePlan without any pattern knowledge.
 
 use super::{
-    CoreCarrierInfo, CoreEffectPlan, CoreLoopPlan, CorePhiInfo, CorePlan, DomainPlan,
+    CoreEffectPlan, CoreLoopPlan, CorePhiInfo, CorePlan, DomainPlan,
     ScanWithInitPlan, SplitScanPlan,
 };
 use crate::mir::builder::control_flow::joinir::patterns::router::LoopPatternContext;

src/mir/builder/control_flow/plan/verifier.rs

@@ -1,4 +1,4 @@
-//! Phase 273 P1: PlanVerifier - CorePlan 不変条件検証 (fail-fast)
+//! Phase 273 P3: PlanVerifier - CorePlan 不変条件検証 (fail-fast)
 //!
 //! # Responsibilities
 //!
@@ -6,16 +6,20 @@
 //! - Fail fast on close-but-unsupported patterns
 //! - Prevent silent miscompilation
 //!
-//! # Invariants (V1-V6)
+//! # Invariants (V2-V9)
 //!
-//! - V1: Carrier completeness (name/init_value/step_value present)
 //! - V2: Condition validity (valid ValueId)
 //! - V3: Exit validity (Return in function, Break/Continue in loop)
 //! - V4: Seq non-empty
 //! - V5: If completeness (then_plans non-empty)
 //! - V6: ValueId validity (all ValueIds pre-generated)
+//! - V7: PHI non-empty (loops require at least one carrier)
+//! - V8: Frag entry matches header_bb
+//! - V9: block_effects contains header_bb
+//!
+//! Phase 273 P3: V1 (Carrier completeness) removed with CoreCarrierInfo
 
-use super::{CoreCarrierInfo, CoreEffectPlan, CoreExitPlan, CoreIfPlan, CoreLoopPlan, CorePlan};
+use super::{CoreEffectPlan, CoreExitPlan, CoreIfPlan, CoreLoopPlan, CorePlan};
 use crate::mir::ValueId;
 
 /// Phase 273 P1: PlanVerifier - CorePlan 不変条件検証 (fail-fast)
@@ -132,21 +136,7 @@ impl PlanVerifier {
         Ok(())
     }
 
-    /// V1: Carrier completeness
-    fn verify_carrier(carrier: &CoreCarrierInfo, depth: usize, index: usize) -> Result<(), String> {
-        if carrier.name.is_empty() {
-            return Err(format!(
-                "[V1] Carrier[{}] at depth {} has empty name",
-                index, depth
-            ));
-        }
-
-        Self::verify_value_id_basic(carrier.init_value, depth, &format!("carrier[{}].init_value", index))?;
-        Self::verify_value_id_basic(carrier.step_value, depth, &format!("carrier[{}].step_value", index))?;
-        Self::verify_value_id_basic(carrier.phi_dst, depth, &format!("carrier[{}].phi_dst", index))?;
-
-        Ok(())
-    }
+    // Phase 273 P3: verify_carrier() removed (CoreCarrierInfo replaced by CorePhiInfo)
 
     /// V5: If completeness
     fn verify_if(if_plan: &CoreIfPlan, depth: usize, in_loop: bool) -> Result<(), String> {