Adds complete artifact system with 9 Mistborn-themed artifact types:
mistcloaks, metal vial sets, glass daggers, dueling canes, koloss
swords, obsidian axes, atium beads, copperminds, and lord's seals.
Includes type definitions, templates, visuals, features, feature
groups, and equipment slots. All artifacts have localization.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
