Refactor: Extract JS/TS wrapper scripts from inline strings in scripting_engine.rs

[louis030195]

Problem

scripting_engine.rs contains large JavaScript/TypeScript wrapper scripts embedded as Rust strings using format!() blocks (lines ~970-1030, ~1690-1770, etc.). This makes the code:

• Hard to maintain (no syntax highlighting, no linting)
• Error-prone (escaping issues with {{ and }})
• Difficult to read and review

Proposed Solution

Extract wrapper scripts to external template files using include_str!:

// Include at compile time
const JS_WRAPPER: &str = include_str!("templates/wrapper.js");

// Use string replacement for dynamic parts
let script = JS_WRAPPER
    .replace("{{USER_SCRIPT}}", &script)
    .replace("{{MODULE_SETUP}}", &module_resolution_setup);

File structure

crates/terminator-mcp-agent/src/
├── scripting_engine.rs
└── templates/
    ├── js_wrapper.js
    ├── ts_wrapper.ts
    └── py_wrapper.py

Benefits

• IDE support: Syntax highlighting, linting, formatting for JS/TS/Python
• Easier maintenance: Edit JS as JS, not escaped Rust strings
• Better reviews: Cleaner diffs when modifying wrapper logic
• No runtime cost: include_str! embeds at compile time

Alternatives Considered

1. indoc! macro: Cleaner inline formatting but still strings
2. Template engine (tera/handlebars): Overkill, adds runtime dep
3. Build-time codegen: More complex than needed

Affected Code

• execute_javascript_with_nodejs (~line 970)
• execute_typescript_with_nodejs (~line 1690)
• execute_python_with_bindings (~line 2100)