UnitDebuff(unit, 1, "RAID") ignores CoA custom classes, so on a
Witchdoctor/Templar/etc. hasDebuff was always nil and the unit-frame
border highlight never lit up on curable Poison/Disease/Magic/Curse.
Fix mirrors the auras.lua shim: if ShadowUF.GetCoaDispels() returns a
dispel set, scan UnitDebuff entries manually and match by dispelType.
Expose getCoaDispels on the ShadowUF namespace so highlight.lua can
reuse the single source of truth (COA_CLASS_DISPELS lives in auras.lua).
florian.berthold
andrew6180