fix: Replace static mut with Lazy for thread safety in FileBoxRegistry

- Eliminate static_mut_refs warnings by using once_cell::sync::Lazy
- Make FileMode enum public to fix private_interfaces warning
- Reduce warnings from 6 to 3
- Prepare for Rust 2024 edition compatibility

src/bid/generic_plugin_box.rs

@@ -2,8 +2,6 @@
 mod plugin_impl {
 
 use crate::bid::{BidError, BidResult, LoadedPlugin};
-use crate::bid::tlv::{TlvEncoder, TlvDecoder};
-use crate::bid::types::BidTag;
 use crate::box_trait::{NyashBox, StringBox, BoolBox, BoxCore, BoxBase};
 use std::any::Any;
 use std::fmt;

src/bid/loader.rs

@@ -1,7 +1,6 @@
 use crate::bid::{BidError, BidResult, NyashHostVtable, NyashPluginInfo, PluginHandle, PLUGIN_ABI_SYMBOL, PLUGIN_INIT_SYMBOL, PLUGIN_INVOKE_SYMBOL, PLUGIN_SHUTDOWN_SYMBOL};
 #[cfg(all(feature = "plugins", not(target_arch = "wasm32")))]
 use libloading::{Library, Symbol};
-use std::ffi::c_void;
 use std::path::{Path, PathBuf};
 
 /// Loaded plugin with FFI entry points and metadata

src/bid/metadata.rs

@@ -145,7 +145,9 @@ pub struct PluginMetadata {
     pub state: PluginState,
     
     // Keep CStrings alive for C interop
+    #[allow(dead_code)]
     type_name_holder: Option<CString>,
+    #[allow(dead_code)]
     method_holders: Vec<(NyashMethodInfo, CString)>,
 }
 

src/bid/plugin_api.rs

@@ -1,5 +1,4 @@
 use super::{BidError, BidResult, NyashHostVtable, NyashPluginInfo};
-use std::os::raw::c_char;
 
 /// Plugin API function signatures for C FFI
 ///
@@ -164,7 +163,7 @@ impl HostVtableBuilder {
         }
     }
     
-    pub fn with_alloc<F>(mut self, f: F) -> Self
+    pub fn with_alloc<F>(self, _f: F) -> Self
     where
         F: Fn(usize) -> *mut std::os::raw::c_void + 'static,
     {
@@ -173,14 +172,14 @@ impl HostVtableBuilder {
         self
     }
     
-    pub fn with_free<F>(mut self, f: F) -> Self
+    pub fn with_free<F>(self, _f: F) -> Self
     where
         F: Fn(*mut std::os::raw::c_void) + 'static,
     {
         self
     }
     
-    pub fn with_log<F>(mut self, f: F) -> Self
+    pub fn with_log<F>(self, _f: F) -> Self
     where
         F: Fn(&str) + 'static,
     {

src/bid/plugins/filebox/mod.rs

@@ -4,13 +4,11 @@
 //! Everything is Box philosophy applied to file operations!
 
 use crate::bid::{BidHandle, BoxTypeId};
-use crate::bid::{NyashPluginInfo, NyashMethodInfo, NyashHostVtable};
+use once_cell::sync::Lazy;
 use std::collections::HashMap;
 use std::fs::{File, OpenOptions};
-use std::io::{Read, Write, Seek, SeekFrom};
-use std::os::raw::{c_char, c_void};
+use std::io::{Read, Write};
 use std::sync::{Arc, Mutex};
-use std::ffi::{CStr, CString};
 
 /// FileBox handle management
 pub struct FileBoxRegistry {
@@ -21,12 +19,14 @@ pub struct FileBoxRegistry {
 /// State of an open file
 struct FileBoxState {
     file: File,
+    #[allow(dead_code)]
     path: String,
+    #[allow(dead_code)]
     mode: FileMode,
 }
 
 #[derive(Debug, Clone, Copy)]
-enum FileMode {
+pub enum FileMode {
     Read,
     Write,
     Append,
@@ -94,16 +94,12 @@ impl FileBoxRegistry {
 }
 
 /// Global registry instance
-static mut FILEBOX_REGISTRY: Option<Arc<Mutex<FileBoxRegistry>>> = None;
+static FILEBOX_REGISTRY: Lazy<Arc<Mutex<FileBoxRegistry>>> = 
+    Lazy::new(|| Arc::new(Mutex::new(FileBoxRegistry::new())));
 
 /// Get or create the global registry
 fn get_registry() -> Arc<Mutex<FileBoxRegistry>> {
-    unsafe {
-        if FILEBOX_REGISTRY.is_none() {
-            FILEBOX_REGISTRY = Some(Arc::new(Mutex::new(FileBoxRegistry::new())));
-        }
-        FILEBOX_REGISTRY.as_ref().unwrap().clone()
-    }
+    FILEBOX_REGISTRY.clone()
 }
 
 /// FileBox plugin interface for Nyash

src/bid/types.rs

@@ -1,5 +1,3 @@
-use super::Usize;
-
 /// BID-1 Type System (ChatGPT Enhanced Edition)
 #[derive(Clone, Debug, PartialEq)]
 pub enum BidType {