Reconcile a reconnecting task feed

Implement reconcile(events). Each event is (sequence, state) for one task. Accept events in any arrival order, collapse exact duplicates, and apply consecutive sequence numbers starting at 1. Sequence 1 must be submitted. Reject conflicting duplicates, gaps, unknown states, booleans used as integers, and invalid transitions. Return the final state, or None for an empty feed. This is an educational application reducer, not an A2A implementation.