fix: send raw ArrayBuffer as binary instead of JSON

[dajiaohuang]

Summary

Fixes #7362

res.send(ArrayBuffer) was sending {} with Content-Type: application/json because ArrayBuffer.isView() returns false for raw ArrayBuffer, causing it to fall through to this.json().

Problem

ArrayBuffer.isView() only returns true for TypedArray views (like Uint8Array), but raw ArrayBuffer is not a view, so it falls through to this.json(chunk) producing {}.

Solution

Add instanceof ArrayBuffer check to handle raw ArrayBuffer like TypedArray views:

• Set Content-Type to 'bin' (binary)
• Convert ArrayBuffer to Buffer before sending

Verification

res.send(new ArrayBuffer(10))
// Before: {} with Content-Type: application/json
// After: 10 zero bytes with Content-Type: application/octet-stream

[krzysdz]

Duplicate of #7363