Apply ChatGPT's FileBox method_id fixes and add build scripts

- Add plugin host initialization for LLVM mode (fixes method_id injection)
- Add FileBox method_id injection test
- Enhance MIR14 stability test
- Add warning for Mock LLVM implementation
- Create build scripts for JIT/LLVM with proper settings (24 threads, timeout)
- Update CLAUDE.md with build instructions and FileBox test results

Note: FileBox file I/O still not working in LLVM execution (separate issue)

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

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

src/runner/modes/llvm.rs

@@ -6,6 +6,9 @@ use std::{fs, process};
 impl NyashRunner {
     /// Execute LLVM mode (split)
     pub(crate) fn execute_llvm_mode(&self, filename: &str) {
+        // Initialize plugin host so method_id injection can resolve plugin calls
+        crate::runner_plugin_init::init_bid_plugins();
+
         // Read the file
         let code = match fs::read_to_string(filename) {
             Ok(content) => content,