Darenfell 0.1.36 - Exploration & Progression Balance Pass

Common Blue Skies magical-material yields normalized:
- Dungeon/common family: Arcane Essence 2-5 -> 1-4
- Cave spawner family: Arcane Essence 2-5 -> 1-3
- Bunker common: Arcane Essence 2-5 -> 1-4

Unchanged: key/progression chests, rare bunker, Undergarden Catacombs, Nexus Sculk Stronghold, Astral major/Postrum, vanilla late-game, specialized spellbooks.
