ArrayBuffer.isView / util.types.isArrayBufferView / isUint8Array return false for a Node Buffer (breaks bson UUID decode in mongodb) #11239

Summary

ArrayBuffer.isView(buf), util.types.isArrayBufferView(buf) and util.types.isUint8Array(buf) all return false for a Node Buffer under Perry. Node returns true for all three (a Buffer is a Uint8Array). buf instanceof Uint8Array is already true under Perry, so only these predicates are wrong.

Repro (no packages)

import { types } from "node:util";

const buf = Buffer.alloc(4);
const isView = ArrayBuffer.isView;
console.log(ArrayBuffer.isView(buf));             // direct call
console.log(isView(buf));                         // through the value (thunk path)
console.log(types.isArrayBufferView(buf));
console.log(types.isUint8Array(buf));
console.log(ArrayBuffer.isView(Buffer.from("abc")));
console.log(ArrayBuffer.isView(buf.subarray(1, 3)));
console.log(ArrayBuffer.isView(Buffer.from(new ArrayBuffer(32), 8, 16)));
console.log(ArrayBuffer.isView(new Uint8Array(4))); // control
console.log(buf instanceof Uint8Array);             // control

Checked with PERRY_NO_AUTO_OPTIMIZE=1 on perrymaster (linux-x64).

Where

• The direct call ArrayBuffer.isView(x) lowers to util/types.isArrayBufferView (crates/perry-hir/src/lower/expr_call/module_static.rs).
• js_util_types_is_array_buffer_view (crates/perry-runtime/src/object/util_types.rs) accepts is_uint8array_buffer(addr) || is_data_view(addr) || typed_array_kind(..). None of these recognise a BufferHeader registered only through register_buffer (is_registered_buffer), which is what Buffer.alloc / Buffer.from / buf.subarray produce.
• array_buffer_is_view_thunk (crates/perry-runtime/src/object/global_this/typed_array.rs) has the same predicate, so the value-call form fails the same way.
• js_util_types_is_uint8_array goes through jsvalue_typed_array_kind only, which also misses Buffers.

Real-world impact

This breaks the npm mongodb driver compiled from source. bson 7.3.3 decodes every binary subtype-4 value (UUID) as new UUID(buffer.subarray(...)), and UUID's constructor accepts the bytes only if ArrayBuffer.isView(input) && input.byteLength === 16. Under Perry that check is false, so the constructor throws:

BSONError: Argument passed in UUID constructor must be a UUID, a 16 byte Buffer or a 32/36 character hex string ...

A plain db.listCollections().toArray() hits it, because the server includes each collection's info.uuid. So does reading back any document that stores a UUID. This is the only failure left in a broad mongodb 7.5.0 probe (CRUD, cursors, bulkWrite, indexes, aggregate, transactions, change streams) run against mongod 8.0.4. It is what blocks removing the native perry-ext-mongodb binding.