🔧 Fix all unused_mut warnings: 16 instances cleaned up

- Remove unnecessary 'mut' from variable declarations
- Clean up code in boxes/, interpreter/, mir/, backend/, and runtime/
- No functional changes, just cleaner code

src/backend/llvm/compiler/codegen.rs

@@ -245,7 +245,7 @@ impl LLVMCompiler {
 
         // Pre-create allocas for locals on demand (entry-only builder)
         let mut allocas: HashMap<ValueId, PointerValue> = HashMap::new();
-        let mut entry_builder = codegen.context.create_builder();
+        let entry_builder = codegen.context.create_builder();
         entry_builder.position_at_end(entry_bb);
 
         // Helper: map MirType to LLVM basic type (value type)
@@ -807,7 +807,7 @@ impl LLVMCompiler {
                             let mut a2 = i64t.const_zero();
                             let mut a3 = i64t.const_zero();
                             let mut a4 = i64t.const_zero();
-                            let mut get_i64 =
+                            let get_i64 =
                                 |vid: ValueId| -> Result<inkwell::values::IntValue, String> {
                                     let v = *vmap.get(&vid).ok_or("arg missing")?;
                                     to_i64_any(codegen.context, &codegen.builder, v)

src/boxes/aot_compiler_box.rs

@@ -31,7 +31,7 @@ impl AotCompilerBox {
             Err(e) => return Box::new(StringBox::new(format!("ERR: current_exe(): {}", e)))
         };
         // Propagate relevant envs (AOT/JIT observe)
-        let mut c = cmd.arg("--backend").arg("vm") // ensures runner path
+        let c = cmd.arg("--backend").arg("vm") // ensures runner path
                       .arg("--compile-native")
                       .arg("-o").arg(out)
                       .arg(file)

src/boxes/p2p_box.rs

@@ -108,7 +108,7 @@ impl P2PBox {
         // Create transport and attach receive callback before boxing
         let (transport_boxed, attach_cb): (Box<dyn Transport>, bool) = match transport_kind {
             TransportKind::InProcess => {
-                let mut t = InProcessTransport::new(node_id.clone());
+                let t = InProcessTransport::new(node_id.clone());
                 // We'll attach callback below after P2PBox struct is created
                 (Box::new(t), true)
             }

src/boxes/socket_box.rs

@@ -215,7 +215,7 @@ impl SocketBox {
         if ms == 0 { return self.accept(); }
 
         let start = std::time::Instant::now();
-        if let Ok(mut guard) = self.listener.write() {
+        if let Ok(guard) = self.listener.write() {
             if let Some(ref listener) = *guard {
                 let _ = listener.set_nonblocking(true);
                 loop {
@@ -319,7 +319,7 @@ impl SocketBox {
         let stream_guard = self.stream.write().unwrap();
         if let Some(ref stream) = *stream_guard {
             match stream.try_clone() {
-                Ok(mut stream_clone) => {
+                Ok(stream_clone) => {
                     drop(stream_guard);
                     let _ = stream_clone.set_read_timeout(Some(Duration::from_millis(ms)));
                     let mut reader = BufReader::new(stream_clone);

src/interpreter/core.rs

@@ -98,7 +98,7 @@ impl NyashInterpreter {
             reg.register(udf);
         }
 
-        let mut this = Self {
+        let this = Self {
             shared,
             local_vars: HashMap::new(),
             outbox_vars: HashMap::new(),
@@ -168,7 +168,7 @@ impl NyashInterpreter {
             reg.register(udf);
         }
 
-        let mut this = Self {
+        let this = Self {
             shared,
             local_vars: HashMap::new(),
             outbox_vars: HashMap::new(),

src/interpreter/objects/fields.rs

@@ -102,7 +102,7 @@ impl NyashInterpreter {
         let mut all_methods = HashMap::new();
         for parent_name in &box_decl.extends {
             use crate::box_trait::is_builtin_box;
-            let mut is_builtin = is_builtin_box(parent_name);
+            let is_builtin = is_builtin_box(parent_name);
             #[cfg(all(feature = "gui", not(target_arch = "wasm32")))]
             {
                 if parent_name == "EguiBox" { is_builtin = true; }

src/mir/builder/stmts.rs

@@ -137,7 +137,7 @@ impl super::MirBuilder {
         // does not assign the same variable, bind that variable to a Phi of (then_value, pre_if_value).
         let assigned_var_then = extract_assigned_var(&then_ast_for_analysis);
         let assigned_var_else = else_ast_for_analysis.as_ref().and_then(|a| extract_assigned_var(a));
-        let mut result_val = self.value_gen.next();
+        let result_val = self.value_gen.next();
         if let Some(var_name) = assigned_var_then.clone() {
             let else_assigns_same = assigned_var_else.as_ref().map(|s| s == &var_name).unwrap_or(false);
             if !else_assigns_same {

src/runtime/plugin_loader_v2/enabled/loader.rs

@@ -173,8 +173,8 @@ impl PluginLoaderV2 {
         let plugins = self.plugins.read().unwrap();
         let plugin = plugins.get(lib_name).ok_or(BidError::PluginError)?;
         let type_id = if let Some(spec) = self.box_specs.read().unwrap().get(&(lib_name.to_string(), box_type.to_string())) { spec.type_id.unwrap_or_else(|| config.box_types.get(box_type).copied().unwrap_or(0)) } else { let box_conf = config.get_box_config(lib_name, box_type, &toml_value).ok_or(BidError::InvalidType)?; box_conf.type_id };
-        let mut out = vec![0u8; 1024];
-        let mut out_len = out.len();
+        let out = vec![0u8; 1024];
+        let out_len = out.len();
         let tlv_args = crate::runtime::plugin_ffi_common::encode_empty_args();
         let (birth_result, _len, out_vec) = super::host_bridge::invoke_alloc(plugin.invoke_fn, type_id, 0, 0, &tlv_args);
         let out = out_vec;