Fix Rust 2024 export-attribute breakage in rebuild-wasm

[Copilot]

rebuild-wasm failed after moving the WASM crate to Rust 2024 because exported FFI symbols still used #[no_mangle], which is now treated as an unsafe attribute. The workflow stopped in wasm-build before regenerating downstream artifacts.

• Root cause addressed

  • Updated all exported WASM FFI functions in wasm-build/src/lib.rs from #[no_mangle] to #[unsafe(no_mangle)] to match Rust 2024 requirements.

• Rust 2024 compatibility adjustment

  • Added crate-level #![allow(static_mut_refs)] for the existing single-threaded WASM global-handle pattern (PARSERS, TREES, NODES, RESULT_BUF) so the module continues compiling under the stricter edition lints without redesigning runtime state management.

• Representative change

  // before
  #[no_mangle]
  pub extern "C" fn parser_new() -> i32 { ... }
  
  // after
  #[unsafe(no_mangle)]
  pub extern "C" fn parser_new() -> i32 { ... }