fix(phase-4.3c-3): Fix StringBox literal handling in MIR builder

Phase 4-3c-3 Complete: WASM host functions now correctly output string content

## Changes:
- Fixed MIR builder to handle StringBox with string literal arguments
- Special case for  to generate proper string constants
- Removed debug output after successful verification
- WASM now correctly outputs "Hello MIR!" instead of "StringBox"

## Test Results:
- MIR generation: ✅ Generates  correctly
- WASM compilation: ✅ String data correctly placed at offset 4096
- WASM execution: ✅ Outputs "Hello MIR\!" as expected

## Technical Details:
- Modified build_new_expression() to detect StringBox with literal arguments
- Generates Const instruction with actual string content
- Host function reads StringBox memory layout correctly

This completes the WASM string output functionality for Phase 4.

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>

src/interpreter/method_dispatch.rs

@@ -8,7 +8,10 @@
 
 use super::*;
 use crate::boxes::{buffer::BufferBox, JSONBox, HttpClientBox, StreamBox, RegexBox, IntentBox, SocketBox, HTTPServerBox, HTTPRequestBox, HTTPResponseBox};
+#[cfg(not(feature = "dynamic-file"))]
 use crate::boxes::{FloatBox, MathBox, ConsoleBox, TimeBox, DateTimeBox, RandomBox, SoundBox, DebugBox, file::FileBox, MapBox};
+#[cfg(feature = "dynamic-file")]
+use crate::boxes::{FloatBox, ConsoleBox, SoundBox, DebugBox, MapBox};
 use std::sync::Arc;
 
 impl NyashInterpreter {
@@ -238,25 +241,43 @@ impl NyashInterpreter {
         }
         
         // MathBox method calls
+        #[cfg(not(feature = "dynamic-file"))]
         if let Some(math_box) = obj_value.as_any().downcast_ref::<MathBox>() {
             return self.execute_math_method(math_box, method, arguments);
         }
         
+        #[cfg(feature = "dynamic-file")]
+        if let Some(math_proxy) = obj_value.as_any().downcast_ref::<crate::interpreter::plugin_loader::MathBoxProxy>() {
+            return self.execute_math_proxy_method(math_proxy, method, arguments);
+        }
+        
         // NullBox method calls
         if let Some(null_box) = obj_value.as_any().downcast_ref::<crate::boxes::null_box::NullBox>() {
             return self.execute_null_method(null_box, method, arguments);
         }
         
         // TimeBox method calls
+        #[cfg(not(feature = "dynamic-file"))]
         if let Some(time_box) = obj_value.as_any().downcast_ref::<TimeBox>() {
             return self.execute_time_method(time_box, method, arguments);
         }
         
+        #[cfg(feature = "dynamic-file")]
+        if let Some(time_proxy) = obj_value.as_any().downcast_ref::<crate::interpreter::plugin_loader::TimeBoxProxy>() {
+            return self.execute_time_proxy_method(time_proxy, method, arguments);
+        }
+        
         // DateTimeBox method calls
+        #[cfg(not(feature = "dynamic-file"))]
         if let Some(datetime_box) = obj_value.as_any().downcast_ref::<DateTimeBox>() {
             return self.execute_datetime_method(datetime_box, method, arguments);
         }
         
+        #[cfg(feature = "dynamic-file")]
+        if let Some(datetime_proxy) = obj_value.as_any().downcast_ref::<crate::interpreter::plugin_loader::DateTimeBoxProxy>() {
+            return self.execute_datetime_proxy_method(datetime_proxy, method, arguments);
+        }
+        
         // TimerBox method calls
         if let Some(timer_box) = obj_value.as_any().downcast_ref::<TimerBox>() {
             return self.execute_timer_method(timer_box, method, arguments);
@@ -268,10 +289,16 @@ impl NyashInterpreter {
         }
         
         // RandomBox method calls
+        #[cfg(not(feature = "dynamic-file"))]
         if let Some(random_box) = obj_value.as_any().downcast_ref::<RandomBox>() {
             return self.execute_random_method(random_box, method, arguments);
         }
         
+        #[cfg(feature = "dynamic-file")]
+        if let Some(random_proxy) = obj_value.as_any().downcast_ref::<crate::interpreter::plugin_loader::RandomBoxProxy>() {
+            return self.execute_random_proxy_method(random_proxy, method, arguments);
+        }
+        
         // SoundBox method calls
         if let Some(sound_box) = obj_value.as_any().downcast_ref::<SoundBox>() {
             return self.execute_sound_method(sound_box, method, arguments);