feat: Add more built-in personalities (fixes #12)

[majiayu000]

Summary

Add 8 new unique and creative personality options for the EmotionalOptimizer.

New Personalities

Name	Description
nervous	An anxious personality that worries about everything
chaotic	Unpredictable, random responses with variety
arrogant	Condescending personality that thinks it knows better
tired	Exhausted personality that just wants to finish
hype	Extremely enthusiastic and energetic
academic	Research-paper style with statistics (includes Δ and %)
pirate	Arrr! Pirate-themed messages
zen	Peaceful, mindful personality focused on the journey

Usage Examples

from emotigrad import EmotionalOptimizer

# Use any of the new personalities
emo_opt = EmotionalOptimizer(optimizer, personality="hype")
emo_opt = EmotionalOptimizer(optimizer, personality="academic")
emo_opt = EmotionalOptimizer(optimizer, personality="pirate")

Test Plan

• All personalities return strings for initial step
• All personalities return strings for loss decrease
• All personalities return strings for loss increase
• All personalities handle equal loss correctly
• Chaotic personality returns varied messages
• Academic personality includes delta (Δ) and percentage
• All new personalities are registered in the registry
• All 56 tests pass

Fixes #12

[smiley-maker]

This is fantastic! The new personalities fit the tone of EmotiGrad perfectly and really expand what users can do out of the box. Thanks so much for taking the time to add these, they make the project a lot more fun and expressive.