Generated Node byte-array arguments do not match emitted RustBuffer ffi signatures

[criccomini]

Summary

For some Node bindings, generated call sites pass the raw result of FfiConverterBytes.lower(...) into ffi-rs calls even though the emitted ffi signatures for those parameters expect UniffiRustBufferStruct.

Repro

Generate Node bindings with uniffi-bindgen-node generate ... for a UniFFI API that takes byte-array arguments. In the generated slatedb-node.ts, call sites look like:

let keyArg = FfiConverterBytes.lower(key);
...
FFI_DYNAMIC_LIB.uniffi_...([..., keyArg]);

But in the generated slatedb-sys.ts, the corresponding ffi signature expects a Rust buffer struct:

uniffi_..._db_delete: (args: [
  /* handle */ bigint,
  /* key */ UniffiRustBufferStruct
]) => bigint

Why this looks inconsistent

FfiConverterBytes.lower(...) comes from AbstractFfiConverterByteArray.lower() and returns UniffiByteArray / Uint8Array, not UniffiRustBufferStruct.

So the generated call site shape is:

• lowered value: Uint8Array
• emitted ffi param type: UniffiRustBufferStruct

Expected

The generated call site and emitted ffi signature should agree. If the ffi side expects UniffiRustBufferStruct, the generated call site should wrap the lowered bytes accordingly. If Uint8Array is the intended argument shape, the emitted signature should reflect that.

Current downstream workaround

Consumers currently patch generated code after codegen so byte-array arguments are wrapped into the Rust-buffer struct shape before being passed to ffi-rs.

[criccomini]

This is related to #30 and might not be an issue if we address it in that issue.