The deep-review flagged that the feed sidebar's new date single-select
derivation was the one bit of migrated logic without a test, while its sibling
primitives (FilterChipGroup/SegmentedToggle/SortControl) all gained one. Lift
the pure logic into lib/dateFilter (deriveDateKey + applyDateChip), same split
as columnSort, and cover it: dateKey for none/preset/custom/off-preset-value,
the preset toggle-off, the preset-not-active-while-custom-open case, and the
Custom open/close + maxAgeDays clearing. Sidebar now calls the helpers; the
onChange is behaviour-identical (self-E2E'd: preset on/off, Custom editor).
11 new tests (vitest 136 -> 147). gate green. Branch not merged.
peter
003043a989