fix(quickadapter): fail closed on unmeasurable entry history (#193)

fix(quickadapter): fail closed on unmeasurable entry history (#193)

* fix(quickadapter): fail closed on unmeasurable entry history

Reject reversal entries when configured historical confirmation is non-finite, while preserving a valid current-candle exit result for exposure reduction.

* docs(quickadapter): drop internal fallback note from lookback tunable

The reversal_confirmation.lookback_period_candles row documents user-facing
usage; the non-finite historical confirmation fallback is an internal
implementation detail already described in reversal_confirmed's docstring.
Keep the tunable description terse and avoid duplicating internals per the
repository documentation conventions.