Feature request: expand /buddy into a persistent companion system with collectibles

Summary

The April Fools' /buddy feature (egg hatching a small creature that watches you code) is genuinely delightful. It would be great to see this expanded into a persistent companion system with collectible creatures and rarity tiers.

Proposed Feature

• Persistent companions: Let the hatched buddy persist across sessions, not just as a one-day gag
• Multiple companions: Allow hatching additional eggs over time (e.g., tied to coding milestones, streaks, or usage)
• Rarity tiers: Common, rare, epic, legendary companions with different appearances and idle animations
• Companion variety: Different creature types beyond the current hatch, each with unique personality and speech bubble comments

Motivation

The Rook cactus companion and the /buddy egg hatch show there's already infrastructure for fun ambient creatures in the UI. Leaning into this with light gamification would make coding sessions more enjoyable and give users a small reason to smile during long debugging sessions.

This isn't asking for anything that affects core functionality, just a fun layer on top of an already great tool.