Extract dispatchBackupForGroupCore (persist+marshal+send, no enqueue on
failure) from dispatchBackupForGroup. drainOne now calls the core
directly so a failed Send only bumps the existing pending_runs row via
BumpPendingRunAttempt — not create a second row — stopping the
geometric duplication on repeated drain failures.
dispatchBackupForGroup (schedule.fire path) wraps the core and keeps
its enqueue-on-failure behaviour unchanged.
TestDrainPendingBumpsOnSendFailure strengthened: asserts exactly 1 row
remains after a send failure (was tolerating >=1 duplicate rows).
steve
1e212db24e