Correction before schema work: the events table conflated the anti-fraud
business ledger with device telemetry. Decision: ledger_events (signed,
chained, reconciled) holds only business facts; device_events (unsigned,
prunable) holds relay/printer/camera/reader/input telemetry. A raw button
press is telemetry; the entry flow mints a signed vehicle_entry. Drops
input_received-as-signed-event.
New: decisions/event-streams-split, concepts/device-events; updated
append-only-event-chain, index, log.
