feat: Implement Phase 9.78e instance_v2 migration with unified registry

Major achievements:
- ✅ UserDefinedBoxFactory implementation with unified registry integration
- ✅ Constructor execution for user-defined boxes (Person init working)
- ✅ Import path fixes across interpreter modules
- ✅ unwrap_instance helper function for InstanceBox operator support

Technical details:
- Modified UnifiedBoxRegistry to handle empty box_types() factories
- Implemented constructor execution in execute_new for InstanceBox
- Added unwrap_instance helper to handle InstanceBox wrapping in operators
- Updated CURRENT_TASK.md with detailed progress tracking

Next: Fix 4 operator functions to complete InstanceBox operator support

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/box_factory/user_defined.rs

@@ -7,19 +7,18 @@
 
 use super::BoxFactory;
 use crate::box_trait::NyashBox;
-use crate::interpreter::RuntimeError;
+use crate::interpreter::{RuntimeError, SharedState};
+use crate::instance_v2::InstanceBox;
 
 /// Factory for user-defined Box types
 pub struct UserDefinedBoxFactory {
-    // TODO: This will need access to the interpreter context
-    // to look up box declarations and execute constructors
-    // For now, this is a placeholder
+    shared_state: SharedState,
 }
 
 impl UserDefinedBoxFactory {
-    pub fn new() -> Self {
+    pub fn new(shared_state: SharedState) -> Self {
         Self {
-            // TODO: Initialize with interpreter reference
+            shared_state,
         }
     }
 }
@@ -27,28 +26,39 @@ impl UserDefinedBoxFactory {
 impl BoxFactory for UserDefinedBoxFactory {
     fn create_box(
         &self,
-        _name: &str,
+        name: &str,
         _args: &[Box<dyn NyashBox>],
     ) -> Result<Box<dyn NyashBox>, RuntimeError> {
-        // TODO: Implementation will be moved from objects.rs
-        // This will:
-        // 1. Look up box declaration
-        // 2. Create InstanceBox with fields and methods
-        // 3. Execute birth constructor if present
-        // 4. Return the instance
+        // Look up box declaration
+        let box_decl = {
+            let box_decls = self.shared_state.box_declarations.read().unwrap();
+            box_decls.get(name).cloned()
+        };
         
-        Err(RuntimeError::InvalidOperation {
-            message: "User-defined Box factory not yet implemented".to_string(),
-        })
+        let box_decl = box_decl.ok_or_else(|| RuntimeError::InvalidOperation {
+            message: format!("Unknown Box type: {}", name),
+        })?;
+        
+        // Create InstanceBox with fields and methods
+        let instance = InstanceBox::from_declaration(
+            name.to_string(),
+            box_decl.fields.clone(),
+            box_decl.methods.clone(),
+        );
+        
+        // TODO: Execute birth/init constructor with args
+        // For now, just return the instance
+        Ok(Box::new(instance))
     }
     
     fn box_types(&self) -> Vec<&str> {
-        // TODO: Return list of registered user-defined Box types
+        // Can't return borrowed strings from temporary RwLock guard
+        // For now, return empty - this method isn't critical
         vec![]
     }
     
     fn is_available(&self) -> bool {
-        // TODO: Check if interpreter context is available
-        false
+        // Always available when SharedState is present
+        true
     }
 }