S3 ListBuckets response is missing BucketRegion, causing buckets to be hidden in VS Code AWS Toolkit

[juman-y]

ListBuckets does not include BucketRegion inside each Bucket entry, which causes buckets to be hidden in the VS Code AWS Toolkit extension.

The AWS Toolkit for VS Code appears to filter out bucket entries that do not have BucketRegion, so none of the buckets are shown when using fakecloud. The relevant code is here:
https://github.com/aws/aws-toolkit-vscode/blob/master/packages/core/src/shared/clients/s3.ts#L383C1-L383C105

This does not affect the AWS CLI; buckets are listed correctly there.

Expected
> GET http://127.0.0.1:4566/
< 200 OK

<?xml version="1.0" encoding="UTF-8"?>
<ListAllMyBucketsResult xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
	<Owner>
		<ID>123456789012</ID>
		<DisplayName>123456789012</DisplayName>
	</Owner>
	<Buckets>
		<Bucket>
			<Name>bucketname</Name>
			<CreationDate>2026-04-28T00:00:00.000Z</CreationDate>
			<BucketRegion>us-east-1</BucketRegion>
		</Bucket>
	</Buckets>
</ListAllMyBucketsResult>

[vieiralucas]

Hey @juman-y — thanks for the precise repro and the link to the toolkit source.

Shipped in #820 (now on main):

• ListBuckets now emits <BucketRegion> on every <Bucket> entry, so the VS Code AWS Toolkit's region filter no longer hides the buckets.
• While in there, also wired up the rest of the ListBuckets v2 surface that AWS shipped alongside BucketRegion: prefix, bucket-region, max-buckets, and continuation-token query parameters, plus a <ContinuationToken> response cursor for pagination.

The next release will pick this up — cutting it in the next couple of hours, after I also land a fix for #817. Once it's out, just bump your fakecloud image and the toolkit should list your buckets the same way it does against real S3.