feat(plugin): Fix plugin BoxRef return and Box argument support

- Fixed deadlock in FileBox plugin copyFrom implementation (single lock)
- Added TLV Handle (tag=8) parsing in calls.rs for returned BoxRefs
- Improved plugin loader with config path consistency and detailed logging
- Fixed loader routing for proper Handle type_id/fini_method_id resolution
- Added detailed logging for TLV encoding/decoding in plugin_loader_v2

Test docs/examples/plugin_boxref_return.nyash now works correctly:
- cloneSelf() returns FileBox Handle properly
- copyFrom(Box) accepts plugin Box arguments
- Both FileBox instances close and fini correctly

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

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

docs/development/current/phase_9_78e_summary.md

@@ -0,0 +1,82 @@
+# Phase 9.78e: Dynamic Method Dispatch Implementation Summary
+
+## 🎯 Overview
+Phase 9.78e aimed to implement dynamic method dispatch through the `call_method` trait method to unify method calling across all Box types.
+
+## ✅ Completed Tasks
+
+### 1. **NyashBox Trait Enhancement**
+- Added `call_method` to the NyashBox trait in `src/box_trait.rs`
+- Default implementation returns `MethodNotFound` error
+- Signature: `fn call_method(&mut self, method_name: &str, args: Vec<NyashValue>) -> Result<NyashValue, RuntimeError>`
+
+### 2. **StringBox Implementation**
+- Implemented `call_method` in `src/boxes/string_box.rs`
+- Supports all StringBox methods:
+  - `type_name()`, `equals()`, `length()`
+  - `concat()`, `split()`, `toUpperCase()`, `toLowerCase()`
+  - `trim()`, `indexOf()`, `replace()`, `charAt()`, `substring()`
+- Includes argument validation and proper error handling
+
+### 3. **InstanceBox Implementation**
+- Implemented `call_method` in `src/instance_v2.rs` with delegation pattern:
+  1. First checks user-defined methods
+  2. Delegates to inner box for builtin methods
+  3. Handles InstanceBox-specific methods (`getField`, `setField`, `hasMethod`)
+- Enables transparent method calls on wrapped builtin boxes
+
+### 4. **Error Type Updates**
+- Added new RuntimeError variants:
+  - `MethodNotFound { method_name: String, type_name: String }`
+  - `FieldNotFound { field_name: String, class_name: String }`
+
+### 5. **Interpreter Integration (Partial)**
+- Added call_method integration in `src/interpreter/expressions/calls.rs`
+- Implemented type conversion logic for Box<dyn NyashBox> to NyashValue
+- Added debug output for tracking method dispatch flow
+
+## 🚧 Challenges Encountered
+
+### 1. **Type Conversion Complexity**
+- Converting between `Box<dyn NyashBox>`, `Arc<Mutex<dyn NyashBox>>`, and `NyashValue`
+- Current workaround: Direct type-based conversion for basic types
+
+### 2. **Binary Compilation Issues**
+- Several unrelated compilation errors in the binary prevent full testing
+- Library builds successfully with call_method implementation
+
+### 3. **Architecture Considerations**
+- The current Box/NyashValue dual system creates friction
+- Future consideration: Unified value representation system
+
+## 📋 Test Results
+- Basic StringBox creation and string operations work correctly
+- Method calls currently fall back to legacy dispatch system
+- Call_method infrastructure is in place but needs full integration
+
+## 🔮 Next Steps
+
+### Immediate Tasks:
+1. Fix binary compilation errors to enable full testing
+2. Complete NyashValue/Box type conversion helpers
+3. Implement call_method for remaining builtin Box types
+
+### Long-term Improvements:
+1. Consider unified value representation to simplify type conversions
+2. Optimize method dispatch performance
+3. Add comprehensive test coverage for all Box types
+
+## 💡 Key Insights
+- The delegation pattern in InstanceBox successfully enables method calls on wrapped boxes
+- Dynamic dispatch through call_method provides a clean abstraction for method calling
+- Type conversion between the Box trait system and NyashValue remains a key challenge
+
+## 📝 Code Locations
+- Trait definition: `src/box_trait.rs:124-130`
+- StringBox impl: `src/boxes/string_box.rs:160-313`
+- InstanceBox impl: `src/instance_v2.rs:197-263`
+- Interpreter integration: `src/interpreter/expressions/calls.rs:230-288`
+
+---
+
+*Phase 9.78e establishes the foundation for unified method dispatch across all Nyash Box types, with the core infrastructure successfully implemented and ready for expanded integration.*