ResultBox migration complete: remove legacy box_trait::ResultBox

- Delete deprecated ResultBox implementation from box_trait.rs
- All code paths use boxes::result::NyashResultBox (aka boxes::ResultBox)
- Tests remain green (179)
- Mark phase 9.78h acceptance: ResultBox移行完了 as done

src/box_trait.rs

@@ -719,159 +719,6 @@ impl Display for ErrorBox {
     }
 }
 
-/// Result values in Nyash - represents success or error results
-#[deprecated(note = "Use boxes::result::NyashResultBox (aka boxes::ResultBox) instead")]
-#[derive(Debug)]
-pub struct ResultBox {
-    pub is_success: bool,
-    pub value: Option<Box<dyn NyashBox>>,
-    pub error: Option<ErrorBox>,
-    base: BoxBase,
-}
-
-#[allow(deprecated)]
-impl ResultBox {
-    pub fn new_success(value: Box<dyn NyashBox>) -> Self {
-        Self {
-            is_success: true,
-            value: Some(value),
-            error: None,
-            base: BoxBase::new(),
-        }
-    }
-    
-    pub fn new_error(error: ErrorBox) -> Self {
-        Self {
-            is_success: false,
-            value: None,
-            error: Some(error),
-            base: BoxBase::new(),
-        }
-    }
-    
-    // ===== Result Methods for Nyash =====
-    
-    /// Check if result is successful
-    pub fn is_ok(&self) -> Box<dyn NyashBox> {
-        Box::new(BoolBox::new(self.is_success))
-    }
-    
-    /// Get success value (returns void if error)
-    pub fn get_value(&self) -> Box<dyn NyashBox> {
-        match &self.value {
-            Some(val) => val.clone_box(),
-            None => Box::new(VoidBox::new()),
-        }
-    }
-    
-    /// Get error (returns void if success)
-    pub fn get_error(&self) -> Box<dyn NyashBox> {
-        match &self.error {
-            Some(err) => Box::new(err.clone()),
-            None => Box::new(VoidBox::new()),
-        }
-    }
-}
-
-#[allow(deprecated)]
-impl BoxCore for ResultBox {
-    fn box_id(&self) -> u64 {
-        self.base.id
-    }
-    
-    fn parent_type_id(&self) -> Option<std::any::TypeId> {
-        self.base.parent_type_id
-    }
-    
-    fn fmt_box(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
-        write!(f, "{}", self.to_string_box().value)
-    }
-    
-    fn as_any(&self) -> &dyn Any {
-        self
-    }
-    
-    fn as_any_mut(&mut self) -> &mut dyn Any {
-        self
-    }
-}
-
-#[allow(deprecated)]
-impl NyashBox for ResultBox {
-    fn to_string_box(&self) -> StringBox {
-        if self.is_success {
-            if let Some(value) = &self.value {
-                StringBox::new(format!("Result(OK: {})", value.to_string_box().value))
-            } else {
-                StringBox::new("Result(OK: void)".to_string())
-            }
-        } else {
-            if let Some(error) = &self.error {
-                StringBox::new(format!("Result(Error: {})", error.to_string_box().value))
-            } else {
-                StringBox::new("Result(Error: unknown)".to_string())
-            }
-        }
-    }
-    
-    fn equals(&self, other: &dyn NyashBox) -> BoolBox {
-        if let Some(other_result) = other.as_any().downcast_ref::<ResultBox>() {
-            if self.is_success != other_result.is_success {
-                return BoolBox::new(false);
-            }
-            
-            if self.is_success {
-                // Compare success values
-                match (&self.value, &other_result.value) {
-                    (Some(a), Some(b)) => a.equals(b.as_ref()),
-                    (None, None) => BoolBox::new(true),
-                    _ => BoolBox::new(false),
-                }
-            } else {
-                // Compare errors
-                match (&self.error, &other_result.error) {
-                    (Some(a), Some(b)) => a.equals(b),
-                    (None, None) => BoolBox::new(true),
-                    _ => BoolBox::new(false),
-                }
-            }
-        } else {
-            BoolBox::new(false)
-        }
-    }
-    
-    fn type_name(&self) -> &'static str {
-        "ResultBox"
-    }
-    
-    fn clone_box(&self) -> Box<dyn NyashBox> {
-        if self.is_success {
-            if let Some(value) = &self.value {
-                Box::new(ResultBox::new_success(value.clone_box()))
-            } else {
-                Box::new(ResultBox::new_success(Box::new(VoidBox::new())))
-            }
-        } else {
-            if let Some(error) = &self.error {
-                Box::new(ResultBox::new_error(error.clone()))
-            } else {
-                Box::new(ResultBox::new_error(ErrorBox::new("Unknown", "Unknown error")))
-            }
-        }
-    }
-    
-    /// 仮実装: clone_boxと同じ（後で修正）
-    fn share_box(&self) -> Box<dyn NyashBox> {
-        self.clone_box()
-    }
-}
-
-#[allow(deprecated)]
-impl Display for ResultBox {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        self.fmt_box(f)
-    }
-}
 
 // FutureBox is now implemented in src/boxes/future/mod.rs using RwLock pattern
 // and re-exported from src/boxes/mod.rs as both NyashFutureBox and FutureBox