The personal-record pass, every half hour for every account, read every
live row of each cumulative type into memory to find the best day. With
784 000 active-energy rows on one account (the per-sample rows pile up
when the nightly drain cannot finish, #1031) it ran a 524 MB heap out of
memory; the old code needed 1.1 GB of heap for that account.
It now reads the type in bounded keyset pages and handles one local day
at a time. The canonical-source pick it applies is per day, so the day
totals and the winner are the same; a tie still keeps the earliest day.
Measured on the same account: 189 MB peak heap, the same record. The
warm-up gate counts only up to its threshold instead of counting a whole
history.
`iterateSourcePages` and `iterateDayBuckets` in the consolidation base
take the row type as a parameter, and the day grouping can keep every row.
