fix(storage): raise StorageApiError when a bucket error body is unrecognized

[tushardev-365]

What

StorageBucketAPI._request indexed the parsed error body directly:

except HTTPStatusError as exc:
    resp = exc.response.json()
    raise StorageApiError(resp["message"], resp["error"], resp["statusCode"]) from exc

So a storage error whose JSON body is missing any of message / error / statusCode came back as a bare KeyError, and a body that isn't JSON at all (an HTML page from a proxy or gateway) came back as a JSONDecodeError. Either way the caller lost the real status and body and got an opaque exception instead of StorageApiError — on the one path where the message matters most. This affects every bucket operation: list_buckets, get_bucket, create_bucket, update_bucket, empty_bucket, delete_bucket.

Fix

Wrap the lookup and fall back to StorageApiError carrying the raw response text, mirroring the shape file_api._request already uses and the ValidationError fallback request.py uses for vector buckets.

Tests

Two new cases per flavour (async + sync), asserting StorageApiError rather than the leaked exception:

• error body missing the expected keys
• error body that isn't JSON

Reverting only the source change makes all four fail with the raw KeyError / JSONDecodeError; with the fix the bucket suite is 28 passed.

Note

#1563 reports this same class of bug in file_api._request (its recovery path reaches for resp.text on a dict), and there are already PRs open for that file. This PR is the bucket API only, which is a separate _request with no recovery path at all — so the two don't overlap.

_sync is generated, so the change was made in _async and regenerated with make build-sync; only the bucket files are included here.