* filer: TUS creation accepts Upload-Concat partial uploads
* filer: TUS final uploads concatenate completed partials
* filer: TUS concatenation tests
* filer: consumed marker pins TUS chunk ownership on completion
* filer: TUS session delete decides chunk ownership after removing the session info
* filer: TUS completion persists the consumed marker before creating the entry
* filer: TUS completion re-verifies the session after persisting the consumed marker
* filer: serialize TUS session ownership transitions per filer
* filer: surface failed TUS consumed-marker rollbacks
