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/mir/builder/schedule/block.rs

@@ -8,11 +8,17 @@ pub struct BlockScheduleBox;
 impl BlockScheduleBox {
     /// Insert a Copy immediately after PHI nodes. Returns the local value id.
     #[allow(dead_code)]
-    pub fn ensure_after_phis_copy(builder: &mut MirBuilder, src: ValueId) -> Result<ValueId, String> {
+    pub fn ensure_after_phis_copy(
+        builder: &mut MirBuilder,
+        src: ValueId,
+    ) -> Result<ValueId, String> {
         if let Some(bb) = builder.current_block {
             if let Some(&cached) = builder.schedule_mat_map.get(&(bb, src)) {
                 if std::env::var("NYASH_SCHEDULE_TRACE").ok().as_deref() == Some("1") {
-                    eprintln!("[schedule/after-phis] bb={:?} src=%{} cached dst=%{}", bb, src.0, cached.0);
+                    eprintln!(
+                        "[schedule/after-phis] bb={:?} src=%{} cached dst=%{}",
+                        bb, src.0, cached.0
+                    );
                 }
                 return Ok(cached);
             }
@@ -31,13 +37,18 @@ impl BlockScheduleBox {
     /// Emit a Copy right before the next emitted instruction (best-effort):
     /// place it at the tail of the current block. Returns the local value id.
     #[allow(dead_code)]
-    pub fn emit_before_call_copy(builder: &mut MirBuilder, src: ValueId) -> Result<ValueId, String> {
+    pub fn emit_before_call_copy(
+        builder: &mut MirBuilder,
+        src: ValueId,
+    ) -> Result<ValueId, String> {
         // Prefer to reuse the after-phis materialized id for this src in this block
         let base = Self::ensure_after_phis_copy(builder, src)?;
         let dst = builder.next_value_id();
         if std::env::var("NYASH_SCHEDULE_TRACE").ok().as_deref() == Some("1") {
-            eprintln!("[schedule/before-call] bb={:?} src=%{} base=%{} dst=%{} (emitting Copy)",
-                builder.current_block, src.0, base.0, dst.0);
+            eprintln!(
+                "[schedule/before-call] bb={:?} src=%{} base=%{} dst=%{} (emitting Copy)",
+                builder.current_block, src.0, base.0, dst.0
+            );
         }
         builder.emit_instruction(MirInstruction::Copy { dst, src: base })?;
         // Propagate metadata to keep dst consistent with base
@@ -54,8 +65,12 @@ impl BlockScheduleBox {
             return;
         }
         let (f_opt, bb_opt) = (builder.current_function.as_ref(), builder.current_block);
-        let (Some(fun), Some(bb_id)) = (f_opt, bb_opt) else { return; };
-        let Some(bb) = fun.get_block(bb_id) else { return; };
+        let (Some(fun), Some(bb_id)) = (f_opt, bb_opt) else {
+            return;
+        };
+        let Some(bb) = fun.get_block(bb_id) else {
+            return;
+        };
 
         // 1) PHI group must be at head
         let mut seen_non_phi = false;
@@ -66,27 +81,27 @@ impl BlockScheduleBox {
                         eprintln!("[block-schedule][verify] WARN: PHI found after non-PHI at bb={:?} idx={}", bb_id, idx);
                     }
                 }
-                _ => { seen_non_phi = true; }
+                _ => {
+                    seen_non_phi = true;
+                }
             }
         }
 
         // 2) If a Copy is immediately before a Call-like, prefer it to be derived from after-PHIs copy
         let is_call_like = |mi: &MirInstruction| -> bool {
-            matches!(mi,
-                MirInstruction::Call { .. } |
-                MirInstruction::BoxCall { .. } |
-                MirInstruction::PluginInvoke { .. } |
-                MirInstruction::ExternCall { .. }
+            matches!(
+                mi,
+                MirInstruction::Call { .. }
+                    | MirInstruction::BoxCall { .. }
+                    | MirInstruction::PluginInvoke { .. }
+                    | MirInstruction::ExternCall { .. }
             )
         };
         for w in bb.instructions.windows(2) {
             if let [MirInstruction::Copy { dst: _, src }, call] = w {
                 if is_call_like(call) {
                     // best-effort: src should be one of the after-PHIs materialized ids for this bb
-                    let derived_ok = builder
-                        .schedule_mat_map
-                        .values()
-                        .any(|&v| v == *src);
+                    let derived_ok = builder.schedule_mat_map.values().any(|&v| v == *src);
                     if !derived_ok {
                         eprintln!(
                             "[block-schedule][verify] WARN: tail Copy src=%{} is not from after-PHIs in bb={:?}",

src/mir/builder/schedule/mod.rs

@@ -1,2 +1 @@
 pub mod block;
-