Sequence continuity

Marking sequences are monotonic feed-local identifiers, not dense counters.

Do not check:

current.sequence === last.sequence + 1n

Instead, check the signed pointer:

current.previousSequence === lastAcceptedSequence

Recommended consumer behavior:

Situation	Action
First snapshot	Accept as current head
Sequence equals or below last accepted	Ignore as duplicate/reordered
previousSequence matches last accepted	Accept as contiguous
previousSequence does not match	Buffer briefly, then replay/resync

Short bursts can arrive out of order. A robust consumer uses a small reorder window before reporting an unresolved gap.

If a gap remains unresolved, reconnect with the last accepted sequence for each feed or request bounded history.