Add [mhenchant]/[ohenchant] weapon temp-enchant conditionals

Uses ClassicAPI's modern C_Item.GetWeaponEnchantInfo (12-tuple with
enchant IDs) plus C_Item.GetEnchantInfo (ID -> localized name) to match
WHICH temporary weapon enchant is applied -- by SpellItemEnchantment ID or
name -- not just that one exists. Locale-proof and exact, unlike
[mhimbue:Name]'s green-text tooltip scan.

ClassicAPI.lua gains GetWeaponEnchant(slot) (centralizes the tuple
indexing, vanilla-global fallback) and GetEnchantName(id). ValidateWeaponImbue
now reads through GetWeaponEnchant. New keywords mhenchant/nomhenchant/
ohenchant/noohenchant support bare (any enchant), single ID/name, and
OR-lists ([mhenchant:2823/Deadly_Poison]); registered in BOOLEAN_CONDITIONALS
for the bare form and auto-added to VALID_CONDITIONALS via Keywords.

Core.lua

@@ -147,6 +147,10 @@ local BOOLEAN_CONDITIONALS = {
     nomhimbue = true,
     ohimbue = true,
     noohimbue = true,
+    mhenchant = true,
+    nomhenchant = true,
+    ohenchant = true,
+    noohenchant = true,
     group = true,
     nogroup = true,
     moving = true,