Add license/copyright notices to top of each source file (where applicable)

src/instructions/gen_tools.rs

@@ -1,3 +1,9 @@
+// Copyright (c) 2025 taitep
+// SPDX-License-Identifier: MIT
+//
+// This file is part of TRVE (https://gitea.taitep.se/taitep/trve)
+// See LICENSE file in the project root for full license text.
+
 use std::hint::unreachable_unchecked;
 
 use crate::instructions::{OpcodeHandler, Splitter};