Critical diagnostic: Our FSDataOutputStream.getPos() override is NOT being called!
Adding WARN logs to SeaweedFileSystemStore.createFile() to determine:
1. Is createFile() being called at all?
2. If yes, but FSDataOutputStream override not called, then streams are
being returned WITHOUT going through SeaweedFileSystem.create/append
3. This would explain why our position tracking fix has no effect
Hypothesis: SeaweedFileSystemStore.createFile() returns SeaweedHadoopOutputStream
directly, and it gets wrapped by something else (not our custom FSDataOutputStream).