chore: Phase 25.1 完了 - LoopForm v2/Stage1 CLI/環境変数削減 + Phase 26-D からの変更

Phase 25.1 完了成果:
- ✅ LoopForm v2 テスト・ドキュメント・コメント完備
  - 4ケース（A/B/C/D）完全テストカバレッジ
  - 最小再現ケース作成（SSAバグ調査用）
  - SSOT文書作成（loopform_ssot.md）
  - 全ソースに [LoopForm] コメントタグ追加

- ✅ Stage-1 CLI デバッグ環境構築
  - stage1_cli.hako 実装
  - stage1_bridge.rs ブリッジ実装
  - デバッグツール作成（stage1_debug.sh/stage1_minimal.sh）
  - アーキテクチャ改善提案文書

- ✅ 環境変数削減計画策定
  - 25変数の完全調査・分類
  - 6段階削減ロードマップ（25→5、80%削減）
  - 即時削除可能変数特定（NYASH_CONFIG/NYASH_DEBUG）

Phase 26-D からの累積変更:
- PHI実装改善（ExitPhiBuilder/HeaderPhiBuilder等）
- MIRビルダーリファクタリング
- 型伝播・最適化パス改善
- その他約300ファイルの累積変更

🎯 技術的成果:
- SSAバグ根本原因特定（条件分岐内loop変数変更）
- Region+next_iパターン適用完了（UsingCollectorBox等）
- LoopFormパターン文書化・テスト化完了
- セルフホスティング基盤強化

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: ChatGPT <noreply@openai.com>
Co-Authored-By: Task Assistant <task@anthropic.com>

src/config/env.rs

@@ -121,7 +121,9 @@ pub fn await_max_ms() -> u64 {
 /// Enable MIR PHI non-generation for Bridge compatibility mode only.
 /// フェーズM.2: MirBuilder/LoopBuilderでPHI統一済み、Bridge層の互換性制御のみ
 /// Default: PHI-ON (Phase 15 direction), override with NYASH_MIR_NO_PHI=1
-pub fn mir_no_phi() -> bool { env_bool("NYASH_MIR_NO_PHI") }
+pub fn mir_no_phi() -> bool {
+    env_bool("NYASH_MIR_NO_PHI")
+}
 
 /// Allow verifier to skip SSA/dominance/merge checks for PHI-less MIR.
 pub fn verify_allow_no_phi() -> bool {
@@ -131,11 +133,15 @@ pub fn verify_allow_no_phi() -> bool {
 /// Enable strict edge-copy policy verification in PHI-off mode.
 /// When enabled, merge blocks must receive merged values via predecessor copies only,
 /// and the merge block itself must not introduce a self-copy to the merged destination.
-pub fn verify_edge_copy_strict() -> bool { env_bool("NYASH_VERIFY_EDGE_COPY_STRICT") }
+pub fn verify_edge_copy_strict() -> bool {
+    env_bool("NYASH_VERIFY_EDGE_COPY_STRICT")
+}
 
 /// Enforce purity of return blocks: no side-effecting instructions allowed before Return
 /// Default: OFF. Enable with NYASH_VERIFY_RET_PURITY=1 in dev/profiling sessions.
-pub fn verify_ret_purity() -> bool { env_bool("NYASH_VERIFY_RET_PURITY") }
+pub fn verify_ret_purity() -> bool {
+    env_bool("NYASH_VERIFY_RET_PURITY")
+}
 
 // ---- LLVM harness toggle (llvmlite) ----
 pub fn llvm_use_harness() -> bool {
@@ -172,7 +178,9 @@ pub fn env_bool_default(key: &str, default: bool) -> bool {
 /// Global fail-fast policy for runtime fallbacks.
 /// Default: ON (true) to prohibit silent/different-route fallbacks in Rust layer.
 /// Set NYASH_FAIL_FAST=0 to temporarily allow legacy fallbacks during bring-up.
-pub fn fail_fast() -> bool { env_bool_default("NYASH_FAIL_FAST", true) }
+pub fn fail_fast() -> bool {
+    env_bool_default("NYASH_FAIL_FAST", true)
+}
 
 // VM legacy by-name call fallback was removed (Phase 2 complete).
 
@@ -204,7 +212,9 @@ pub fn plugin_only() -> bool {
 /// Core-13 "pure" mode: after normalization, only the 13 canonical ops are allowed.
 /// If enabled, the optimizer will try lightweight rewrites for Load/Store/NewBox/Unary,
 /// and the final verifier will reject any remaining non-Core-13 ops.
-pub fn mir_core13_pure() -> bool { env_bool("NYASH_MIR_CORE13_PURE") }
+pub fn mir_core13_pure() -> bool {
+    env_bool("NYASH_MIR_CORE13_PURE")
+}
 
 /// Enable heuristic pre-pin of comparison operands in if/loop headers.
 /// Default: OFF (0). Set NYASH_MIR_PREPIN=1 to enable.
@@ -235,14 +245,26 @@ pub fn opt_diag_fail() -> bool {
 // ---- Legacy compatibility (dev-only) ----
 /// Enable legacy InstanceBox fields (SharedNyashBox map) for compatibility.
 /// Default: OFF. Set NYASH_LEGACY_FIELDS_ENABLE=1 to materialize and use legacy fields.
-pub fn legacy_fields_enable() -> bool { env_bool("NYASH_LEGACY_FIELDS_ENABLE") }
+pub fn legacy_fields_enable() -> bool {
+    env_bool("NYASH_LEGACY_FIELDS_ENABLE")
+}
 
 // ---- GC/Runtime tracing (execution-affecting visibility) ----
-pub fn gc_trace() -> bool { env_bool("NYASH_GC_TRACE") }
-pub fn gc_barrier_trace() -> bool { env_bool("NYASH_GC_BARRIER_TRACE") }
-pub fn runtime_checkpoint_trace() -> bool { env_bool("NYASH_RUNTIME_CHECKPOINT_TRACE") }
-pub fn vm_pic_stats() -> bool { env_bool("NYASH_VM_PIC_STATS") }
-pub fn vm_vt_trace() -> bool { env_bool("NYASH_VM_VT_TRACE") }
+pub fn gc_trace() -> bool {
+    env_bool("NYASH_GC_TRACE")
+}
+pub fn gc_barrier_trace() -> bool {
+    env_bool("NYASH_GC_BARRIER_TRACE")
+}
+pub fn runtime_checkpoint_trace() -> bool {
+    env_bool("NYASH_RUNTIME_CHECKPOINT_TRACE")
+}
+pub fn vm_pic_stats() -> bool {
+    env_bool("NYASH_VM_PIC_STATS")
+}
+pub fn vm_vt_trace() -> bool {
+    env_bool("NYASH_VM_VT_TRACE")
+}
 pub fn vm_pic_trace() -> bool {
     std::env::var("NYASH_VM_PIC_TRACE").ok().as_deref() == Some("1")
 }
@@ -349,7 +371,11 @@ pub fn extern_trace() -> bool {
 // ---- Operator Boxes adopt defaults ----
 /// CompareOperator.apply adopt: default ON (prod/devともに採用)
 pub fn operator_box_compare_adopt() -> bool {
-    match std::env::var("NYASH_OPERATOR_BOX_COMPARE_ADOPT").ok().as_deref().map(|v| v.to_ascii_lowercase()) {
+    match std::env::var("NYASH_OPERATOR_BOX_COMPARE_ADOPT")
+        .ok()
+        .as_deref()
+        .map(|v| v.to_ascii_lowercase())
+    {
         Some(ref s) if s == "0" || s == "false" || s == "off" => false,
         Some(ref s) if s == "1" || s == "true" || s == "on" => true,
         _ => true, // default ON
@@ -357,7 +383,11 @@ pub fn operator_box_compare_adopt() -> bool {
 }
 /// AddOperator.apply adopt: default OFF（順次昇格のため）
 pub fn operator_box_add_adopt() -> bool {
-    match std::env::var("NYASH_OPERATOR_BOX_ADD_ADOPT").ok().as_deref().map(|v| v.to_ascii_lowercase()) {
+    match std::env::var("NYASH_OPERATOR_BOX_ADD_ADOPT")
+        .ok()
+        .as_deref()
+        .map(|v| v.to_ascii_lowercase())
+    {
         Some(ref s) if s == "0" || s == "false" || s == "off" => false,
         _ => true, // default ON (promoted after validation)
     }
@@ -415,9 +445,15 @@ pub fn enable_using() -> bool {
 pub fn using_profile() -> String {
     std::env::var("NYASH_USING_PROFILE").unwrap_or_else(|_| "dev".to_string())
 }
-pub fn using_is_prod() -> bool { using_profile().eq_ignore_ascii_case("prod") }
-pub fn using_is_ci() -> bool { using_profile().eq_ignore_ascii_case("ci") }
-pub fn using_is_dev() -> bool { using_profile().eq_ignore_ascii_case("dev") }
+pub fn using_is_prod() -> bool {
+    using_profile().eq_ignore_ascii_case("prod")
+}
+pub fn using_is_ci() -> bool {
+    using_profile().eq_ignore_ascii_case("ci")
+}
+pub fn using_is_dev() -> bool {
+    using_profile().eq_ignore_ascii_case("dev")
+}
 /// Allow `using "path"` statements in source (dev-only by default).
 pub fn allow_using_file() -> bool {
     // SSOT 徹底: 全プロファイルで既定禁止（nyash.toml を唯一の真実に）
@@ -432,7 +468,11 @@ pub fn allow_using_file() -> bool {
 /// 1) Explicit env `NYASH_USING_AST` = 1/true/on → enabled, = 0/false/off → disabled
 /// 2) Default by profile: dev/ci → ON, prod → OFF
 pub fn using_ast_enabled() -> bool {
-    match std::env::var("NYASH_USING_AST").ok().as_deref().map(|v| v.to_ascii_lowercase()) {
+    match std::env::var("NYASH_USING_AST")
+        .ok()
+        .as_deref()
+        .map(|v| v.to_ascii_lowercase())
+    {
         Some(ref s) if s == "1" || s == "true" || s == "on" => true,
         Some(ref s) if s == "0" || s == "false" || s == "off" => false,
         _ => !using_is_prod(), // dev/ci → true, prod → false
@@ -443,7 +483,11 @@ pub fn using_ast_enabled() -> bool {
 /// - dev/ci: default true (allow, with WARN)
 /// Override with NYASH_VM_USER_INSTANCE_BOXCALL={0|1}
 pub fn vm_allow_user_instance_boxcall() -> bool {
-    match std::env::var("NYASH_VM_USER_INSTANCE_BOXCALL").ok().as_deref().map(|v| v.to_ascii_lowercase()) {
+    match std::env::var("NYASH_VM_USER_INSTANCE_BOXCALL")
+        .ok()
+        .as_deref()
+        .map(|v| v.to_ascii_lowercase())
+    {
         Some(ref s) if s == "0" || s == "false" || s == "off" => false,
         Some(ref s) if s == "1" || s == "true" || s == "on" => true,
         _ => !using_is_prod(),
@@ -630,7 +674,10 @@ fn warn_alias_once(alias: &str, primary: &str) {
     let set = WARNED_ALIASES.get_or_init(|| Mutex::new(HashSet::new()));
     if let Ok(mut s) = set.lock() {
         if !s.contains(alias) {
-            eprintln!("[deprecate/env] '{}' is deprecated; use '{}'", alias, primary);
+            eprintln!(
+                "[deprecate/env] '{}' is deprecated; use '{}'",
+                alias, primary
+            );
             s.insert(alias.to_string());
         }
     }
@@ -652,7 +699,9 @@ pub fn llvm_opt_level() -> String {
 
 /// Gate‑C(Core) route request (primary: NYASH_GATE_C_CORE; alias: HAKO_GATE_C_CORE)
 pub fn gate_c_core() -> bool {
-    if env_bool("NYASH_GATE_C_CORE") { return true; }
+    if env_bool("NYASH_GATE_C_CORE") {
+        return true;
+    }
     if env_bool("HAKO_GATE_C_CORE") {
         warn_alias_once("HAKO_GATE_C_CORE", "NYASH_GATE_C_CORE");
         return true;