refactor(phase124): Delete NYASH_HAKO_CHECK_JOINIR flag completely

- Remove src/config/env/hako_check.rs entirely (file deleted)
- Comment out hako_check module in src/config/env.rs with Phase 124 markers
- Mark NYASH_HAKO_CHECK_JOINIR as deleted in environment-variables.md
- Document reason: JoinIR-only consolidation makes flag unnecessary

Phase 124 Task 2/5 complete

docs/reference/environment-variables.md

@@ -158,7 +158,7 @@ JoinIR は制御構造を関数呼び出し + 継続に正規化する IR 層。
 | `HAKO_JOINIR_IF_IN_LOOP_ENABLE` | OFF | if-in-loop JoinIR 本線切替（Core 候補）。 |
 | `NYASH_JOINIR_VM_BRIDGE` | OFF | VM bridge Route B。Core 判定に含まれる。 |
 | `NYASH_JOINIR_LLVM_EXPERIMENT` | OFF | LLVM 経路 JoinIR 実験（ハーネス専用）。Core 判定に含まれる。 |
-| `NYASH_HAKO_CHECK_JOINIR` | OFF | hako_check で JoinIR 経路を使用（Phase 123+）。Phase 124 で ON がデフォルトに。 |
+| ~~`NYASH_HAKO_CHECK_JOINIR`~~ | 削除済み | **Phase 124 で削除**: hako_check は JoinIR 専用化。環境変数不要。 |
 
 ### DevOnly（開発/計測専用）
 

src/config/env.rs

@@ -5,13 +5,15 @@
 
 mod catalog;
 pub mod dump;
-pub mod hako_check;
+// Phase 124: hako_check module removed (JoinIR-only consolidation)
+// pub mod hako_check;
 pub mod joinir_dev;
 pub mod stage1;
 
 pub use catalog::{env_vars, AppliesTo, EnvVarMeta};
 pub use dump::*;
-pub use hako_check::*;
+// Phase 124: hako_check exports removed (JoinIR-only consolidation)
+// pub use hako_check::*;
 pub use joinir_dev::*;
 pub use stage1::*;
 use std::collections::BTreeMap;