Add Sanctum of Fruitful Harvest

[radar]

Summary

• Implements Sanctum of Fruitful Harvest ({2}{G}, Legendary Enchantment — Shrine)
• At the beginning of your first main phase, adds X mana of any one color, where X is the number of Shrines you control
• Uses FirstMainPhaseTrigger and Magic::Choice::Color pattern consistent with other shrine cards

Test plan

• Triggers at beginning of controller's first main phase
• Prompts for color choice (ColorChoice)
• Adds mana equal to the number of Shrines controlled in the chosen color

🤖 Generated with Claude Code