Type Alias VersionEntry

One entry in an ordered version history. entries[i] IS version i: applying its changes over the previous version's schema yields version i, so entries[0] builds version 0 (the initial schema) from the empty base and currentVersion === entries.length - 1. Folding every entry's changes from {} reconstructs the current schema.

Components and resources are patched separately so their namespaces stay distinct (a Schema can't say which it is) and so a component↔resource move is expressible as a removal in one plus an add in the other.

handler is present iff the change is not automatically convertible (a major change — a type change, split, cross-component move, …). It runs against the store staged to the schema of version i - 1 — the input this entry transforms — and transforms the data in place. Additive / minor / removal changes carry no handler — load-time conversion handles them.

SINGLE-QUADRANT CONTRACT. A handler touches exactly ONE persisted quadrant — document (shared+persistent) or settings (nonShared+persistent): the one its schema change is in, which the guard enforces. Only THAT quadrant is staged to the version i - 1 shape before the handler runs; the other quadrant is deliberately left unconformed, because per-quadrant versioning lets the two drift to different versions and staging the other one could down-convert it. So a handler must read and write ONLY its own quadrant's components/resources. Reading another quadrant is a silent bug: under a scoped/split load it may be absent or at a different version, so the read returns stale/default data and the migration decides wrong. This is not statically enforced — keep each handler within its own quadrant.