Adds a display-mode pair (全量/增量, Total/Diff) next to the Step/Turn granularity group in the Context History card. Diff mode plots each request's per-category |change| vs the previous request, with the hover tip reporting the signed net change (Δ +1.2k / Δ −535.5k); Total keeps the cumulative composition and stays the default.
Original PR by @xieshuaix (delta toggle); reworked before merge: the on/off delta switch became a two-way mode control (mode: 'total' | 'diff' end to end), the two toggle groups were wrapped so the title's auto-margin push happens once, trend.hint was shortened/localized, and the fiber-slot/button-count tests were updated.
sxgitmiao
be751da48d