A post's allocation rule becomes a dated series: a version takes effect in its
month and continues until the next replaces it. Per-month overrides survive
alongside as one-month exceptions, because collapsing the two loses the
distinction between a permanent change and a temporary one.
A post with no version yet allocates zero rather than applying its earliest
rule backwards, which would invent budget for months never budgeted and let
the rollover fold carry that fiction forward.
Requires the project's first real migration (schemaVersion 1 -> 2). It is a
pure shape change and behaviour-preserving by construction, and the spec makes
that a tested property rather than an assumption: every month's allocation must
be identical before and after.
Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
