Phase 30.1 & 73: Stage-3 features env and JoinIR flag cleanup

src/parser/declarations/box_def/members/postfix.rs

@@ -11,7 +11,7 @@ pub(crate) fn wrap_with_optional_postfix(
     p: &mut NyashParser,
     body: Vec<ASTNode>,
 ) -> Result<Vec<ASTNode>, ParseError> {
-    if !(crate::config::env::parser_stage3()
+    if !(crate::config::env::parser_stage3_enabled()
         && (p.match_token(&TokenType::CATCH) || p.match_token(&TokenType::CLEANUP)))
     {
         return Ok(body);

src/parser/declarations/box_def/mod.rs

@@ -121,7 +121,7 @@ pub fn parse_box_declaration(p: &mut NyashParser) -> Result<ASTNode, ParseError>
     let mut last_method_name: Option<String> = None;
     while !p.match_token(&TokenType::RBRACE) && !p.is_at_end() {
         // 分類（段階移行用の観測）: 将来の分岐移譲のための前処理
-        if crate::config::env::parser_stage3() {
+        if crate::config::env::parser_stage3_enabled() {
             if let Ok(kind) = members::common::classify_member(p) {
                 let _ = kind; // 現段階では観測のみ（無副作用）
             }

src/parser/mod.rs

@@ -159,10 +159,10 @@ impl NyashParser {
     }
 
     /// 文字列からパース (トークナイズ + パース)
-    /// Note: Reads environment variables (NYASH_PARSER_STAGE3, etc.) for using-chain parsing
+    /// Note: Reads parser_stage3_enabled() (NYASH_FEATURES=stage3 or legacy env) for using-chain parsing
     pub fn parse_from_string(input: impl Into<String>) -> Result<ASTNode, ParseError> {
         // Ensure Stage-3 features are enabled when parsing using-chain files
-        // if the parent process has NYASH_PARSER_STAGE3=1 set
+        // when parent requested Stage-3 parsing via NYASH_FEATURES/legacy env
         Self::parse_from_string_with_fuel(input, Some(100_000))
     }
 

src/parser/statements/control_flow.rs

@@ -192,16 +192,7 @@ impl NyashParser {
 
     /// Helper: env-gated Stage-3 enable check.
     fn is_stage3_enabled() -> bool {
-        let on = |key: &str| {
-            std::env::var(key)
-                .ok()
-                .map(|v| {
-                    let lv = v.to_ascii_lowercase();
-                    lv == "1" || lv == "true" || lv == "on"
-                })
-                .unwrap_or(false)
-        };
-        on("NYASH_PARSER_STAGE3") || on("HAKO_PARSER_STAGE3")
+        crate::config::env::parser_stage3_enabled()
     }
 
     /// Parse break statement