* fix(s3): preserve explicit directory markers during empty folder cleanup
PR #8292 switched empty-folder cleanup from per-folder implicit checks
to bucket-level policy, inadvertently dropping the check that preserved
explicitly created directories (e.g., PUT /bucket/folder/). This caused
user-created folders to be deleted when their last file was removed.
Add IsDirectoryKeyObject check in executeCleanup to skip folders that
have a MIME type set, matching the canonical pattern used throughout the
S3 listing and delete handlers.
* fix: handle ErrNotFound in IsDirectoryKeyObject for race safety
Entry may be deleted between the emptiness check and the directory
marker lookup. Treat not-found as false rather than propagating
the error, avoiding unnecessary error logging in the cleanup path.
* refactor: consolidate directory marker tests and tidy error handling
- Combine two separate test functions into a table-driven test
- Nest ErrNotFound check inside the err != nil block
0761be58d3