ConditionEffect gains duration_rounds_per_level and max_duration_rounds
(mirroring PenaltyEffect), applied as caster_level * per_level rounds capped
at max: hold person 1 rd/lvl, doom 1 min/lvl, touch of fatigue 1 rd/lvl,
vanish 1 rd/lvl (max 5). Extend Spell doubles both the per-level rate and
the cap. Tests cover scaling and the vanish cap.