ISS: Additional Spells

Restricted-spell fixes:

• Madness, Dread, Unmake, and Unstable Magic require Eldritch research. Owning a scroll or spellbook doesn’t bypass learning, and Eldritch follows ISS’s native loot rules.
• All 25 spells respect the progression rules of Unraveling the Spells and ISS Restrictions, tested separately. With Unraveling, set enable_eldritch_school_learning = true to use its Magic Lectern for Eldritch; otherwise, use the ISS manuscript.

 Spell changes:

• Purify removes Poison and Wither from you or one ally and briefly keeps them from coming back. Use Cleanse for other harmful effects or to help a group.
• Unmake curses an enemy summon so some of the damage it deals also hurts its summoner. If the summoner isn’t around, Unmake hurts the summon directly.
• Dread creates a fear zone where you aim. Enemies flee until they leave it. Turn Undead still makes nearby undead flee from you.
• Life Tap trades health for a boost to your next spell. If you’re interrupted before the spell goes off, you keep the boost until it expires.
• Blood Sacrifice is now called Sanguine Exchange. It still trades health for mana.
• Spatial Anchor now blocks travel through ISS Portals, portal frames, and Recall into or out of the area. Teleport commands still work.