ctrlrun.state.Consumption — class, defined at src/ctrlrun/state.py:551
consumptions() hands it back (SPEC-v0.9 §3.3.3, §10).
released_at is None while the charge is held. Whether it is held and why is §7.2’s
question, and the answer is a join through get_effect on effect_key rather than a column
here: the ledger deliberately has no state machine of its own (§4.1).