fix(quickadapter): preserve calendar PnL continuity (#142)

fix(quickadapter): preserve calendar PnL continuity (#142)

* fix(quickadapter): preserve calendar PnL continuity

* fix(quickadapter): drop epoch-anchored phase guard in PnL continuity

The (month-1) % n phase guard on the MS path assumed a fixed January
epoch, but pandas resample anchors calendar bins on the data origin, not
a fixed epoch, so it wrongly reset valid non-January-anchored multi-month
series (e.g. a Feb/May/Aug 3M grid). is_on_offset already rejects a
non-boundary stored date and stored + offset is the exact next candle for
any anchor phase, so the membership test alone is correct and symmetric
for MS and YS (resolving the MS/YS asymmetry). Also complete the
_TradeHistory key-mirror comment with the legacy timeframe-minutes key.

* style(quickadapter): tighten PnL continuity phase-guard rationale comment