The cases CSV carries every cycle while the open and staff-closed lists carry one

[Taleef7]

#602 made the cases CSV carry every filter the work list sends, and a frontend test compares the two
query strings so they cannot drift. One width difference is left, and it is the one that test cannot
see: the period default is a server-side default with no query parameter.

What is wrong

isCurrentCycleDefault (backend-ts/src/case/worklist-read-model.ts) makes the open, blank
and staff-closed lists show the per-measure current compliance cycle. /api/exports/cases
applies no period logic at all — §6.3 says so explicitly for staff_closed, and it is true for every
status.

So:

one OPEN case, evaluation_period 2025-01-01 (a prior cycle), nothing else

GET /api/cases?status=open                      → 0 rows, X-Total-Count: 0
GET /api/exports/cases?format=csv&status=open   → contains the case

The screen says "0 cases loaded" and the button under it downloads a file with a row in it.

On ?status=staff_closed this is unbounded rather than incidental: staff closures accumulate across
years, CYCLE_ROLLED_OVER never sweeps them, the tab shows only the current cycle, and its three
header counts describe that cycle — while the CSV taken from it carries every prior year's closures
beside them.

Why it was not fixed in #602

Two reasons, and the second is the real one:

1. It needs a decision rather than a fix. Making the export match the list would change what
   /api/exports/cases has always returned, and the endpoint is documented as all-history (§6.3) —
   something downstream may depend on that. Making the list match the export is obviously wrong.
   A third option is an explicit ?period= on the export plus the button sending the list's default,
   which keeps the endpoint's default behaviour and closes the screen/file gap.
2. The parity test in fix(export): the cases CSV describes the list it was taken from #602 compares query strings. A server-side default appears in neither, so
   whatever is decided here needs a different kind of test — a result-set comparison over one
   fixture, the way ADR-084's two work-list loaders are pinned against each other.

Also in scope, small

site is compared case-sensitively by the list (worklist-read-model.ts, c.site === filters.site)
and case-insensitively by the export (export-csv.ts, both sides lower-cased). Before #602 the
export's site filter was only reachable by hand-writing a URL; now the button sends it on every
export. The practical risk is low — the options are built from the directory's own strings — but a
directory holding two sites differing only in case would export both under a heading naming one.
Pick one comparison and share it, as matchesCaseSearch now is.

Recorded

§6.3 in docs/DATA_MODEL_CONTRACTS.md now states the period difference rather than implying parity,
so nothing in the always-loaded contract claims this is closed.