Collapse the three Compare tabs (MoM / YoY / Budget) into two modes. The
new "Actual vs actual" mode exposes an explicit reference-month dropdown
in the header (defaults to the previous month, wraps around January) and
a MoM/YoY sub-toggle. The chart is rewritten to a grouped side-by-side
BarChart with two bars per category (reference period vs comparison
period) so both values are visible at a glance instead of just the
delta. The URL PeriodSelector stays in sync with the reference month.
- useCompare: state splits into { mode: "actual"|"budget", subMode:
"mom"|"yoy", year, month }. Pure helpers previousMonth(),
defaultReferencePeriod(), comparisonMeta() extracted for tests
- CompareModeTabs: 2 modes instead of 3
- New CompareSubModeToggle and CompareReferenceMonthPicker components
- ComparePeriodChart: grouped bars via two <Bar dataKey="..."/> on a
vertical BarChart
- i18n: modeActual / subModeMoM / subModeYoY / referenceMonth (FR+EN),
retire modeMoM / modeYoY
- 9 new vitest cases covering the pure helpers (January wrap-around for
both MoM and YoY, default reference period, month/year arithmetic)
Closes#96
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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