Object layer of the session-projection RFC client base: ProjectionCellSpec/
ProjectionCell/ProjectionCellSet with the single seq-watermark rule (live and
window-replace events share one filter; baseline reset re-seeds value+watermark
unless a newer commit applied; absent key = capability absent), Session
dispatch at appendLive/installWindow (projections block read structurally,
TODO(gui) switch to the interface package), SessionsService.registerProjectionCell
roster (live scopes now + future scopes at mint; disposer sweeps every session),
and the provideInfo projections face (key-addressed bare cell sources).
15 object-layer specs: watermark no-rollback, late-baseline seq rule,
capability absence, schema-failure degrade, duplicate-key throw, resync e2e.