chore: Remove unused imports in normalized_shadow modules

Cleaned up unused imports after Phase 143 execution fix (5e662eaaf).

**Priority files (Phase 143)**:
- if_as_last_join_k.rs: removed ValueId, BTreeMap
- loop_true_break_once.rs: added #[cfg(test)] for test-only imports
- post_if_post_k.rs: removed ValueId, BTreeMap
- normalized_helpers.rs: added #[cfg(test)] for Span

**Additional cleanup**:
- contract_checks.rs: removed BasicBlockId
- joinir/mod.rs: removed Info struct re-exports (functions kept)
- patterns/mod.rs: removed Info struct re-exports (functions kept)
- ast_feature_extractor.rs: removed EscapeSkipPatternInfo
- plan_box.rs: added #[cfg(test)] for PlanKind

**Verification**:
- 0 unused import warnings (was 20+)
- All 69 normalized_shadow tests pass
- Clean build with --release

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

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

src/mir/control_tree/normalized_shadow/common/normalized_helpers.rs

@@ -9,9 +9,12 @@
 
 use crate::mir::ValueId;
 use crate::mir::join_ir::lowering::join_value_space::{PARAM_MIN, LOCAL_MIN};
-use crate::ast::{ASTNode, Span};
+use crate::ast::ASTNode;
 use std::collections::BTreeMap;
 
+#[cfg(test)]
+use crate::ast::Span;
+
 /// Box-First: Normalized lowering 共通ヘルパー
 pub struct NormalizedHelperBox;
 

src/mir/control_tree/normalized_shadow/exit_reconnector.rs

@@ -58,7 +58,7 @@
 //! - **Normalized-specific**: Only used for Normalized shadow path
 //! - **Fail-Fast**: Panics if carrier not in variable_map (contract violation)
 
-use crate::mir::{BasicBlockId, MirFunction, MirInstruction, ValueId};
+use crate::mir::{BasicBlockId, MirFunction, ValueId};
 use std::collections::BTreeMap;
 
 /// ExitReconnectorBox: Direct variable_map reconnection for Normalized shadow

src/mir/control_tree/normalized_shadow/legacy/mod.rs

@@ -4,7 +4,7 @@ use crate::mir::control_tree::normalized_shadow::env_layout::EnvLayout;
 use crate::mir::control_tree::step_tree::StepTree;
 use crate::mir::control_tree::step_tree_contract_box::StepTreeContract;
 use crate::mir::join_ir::lowering::carrier_info::JoinFragmentMeta;
-use crate::mir::join_ir::{CompareOp, JoinFunction, JoinFuncId, JoinInst, JoinModule, MirLikeInst};
+use crate::mir::join_ir::{CompareOp, JoinFunction, JoinFuncId, JoinModule};
 use crate::mir::ValueId;
 use std::collections::BTreeMap;
 

src/mir/control_tree/normalized_shadow/loop_true_break_once.rs

@@ -51,13 +51,17 @@ use super::common::return_value_lowerer_box::ReturnValueLowererBox;
 use super::common::normalized_helpers::NormalizedHelperBox;
 use super::env_layout::EnvLayout;
 use super::legacy::LegacyLowerer;
-use crate::ast::{ASTNode, LiteralValue};
 use crate::mir::control_tree::step_tree::{StepNode, StepStmtKind, StepTree};
 use crate::mir::join_ir::lowering::carrier_info::JoinFragmentMeta;
 use crate::mir::join_ir::lowering::error_tags;
-use crate::mir::join_ir::{BinOpKind, ConstValue, JoinFunction, JoinFuncId, JoinInst, JoinModule, MirLikeInst};
-use crate::mir::join_ir_vm_bridge::join_func_name;
+use crate::mir::join_ir::{JoinFunction, JoinFuncId, JoinInst, JoinModule};
 use crate::mir::ValueId;
+
+#[cfg(test)]
+use crate::mir::join_ir::{BinOpKind, ConstValue, MirLikeInst};
+#[cfg(test)]
+use crate::mir::join_ir_vm_bridge::join_func_name;
+#[cfg(test)]
 use std::collections::BTreeMap;
 
 /// Box-First: loop(true) break-once lowering to Normalized

src/mir/control_tree/normalized_shadow/post_if_post_k.rs

@@ -36,8 +36,6 @@ use crate::mir::control_tree::step_tree::{StepNode, StepStmtKind, StepTree};
 use crate::mir::join_ir::lowering::carrier_info::JoinFragmentMeta;
 use crate::mir::join_ir::lowering::error_tags;
 use crate::mir::join_ir::{ConstValue, JoinFunction, JoinFuncId, JoinInst, JoinModule, MirLikeInst};
-use crate::mir::ValueId;
-use std::collections::BTreeMap;
 
 /// Box-First: Post-if continuation lowering with post_k
 pub struct PostIfPostKBuilderBox;
@@ -228,7 +226,7 @@ impl PostIfPostKBuilderBox {
         // post_k(env): <post_stmts> ; Ret
         // Phase 143 fix: reuse Param region IDs for all functions
         let post_k_params = main_params.clone();
-        let mut env_post_k = NormalizedHelperBox::build_env_map(&env_fields, &post_k_params);
+        let env_post_k = NormalizedHelperBox::build_env_map(&env_fields, &post_k_params);
         let mut post_k_func = JoinFunction::new(post_k_id, "post_k".to_string(), post_k_params);
 
         // Lower post-if statements