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>

Cargo.toml

@@ -29,6 +29,11 @@ crate-type = ["cdylib", "rlib"]
 name = "nyash"
 path = "src/main.rs"
 
+# WASM runner executable
+[[bin]]
+name = "nyash-wasm-run"
+path = "src/bin/nyash-wasm-run.rs"
+
 # Examples for development - only available as examples, not bins
 [[example]]
 name = "gui_simple_notepad"
@@ -180,5 +185,6 @@ debug = true
 members = [
     ".",                    # メインのnyash-rustプロジェクト
     "plugins/nyash-file",   # FileBoxプラグイン
+    "plugins/nyash-math",   # Math/Time系プラグイン
 ]
 resolver = "2"