feat: Implement Chooser option pricing model

[joaquinbejar]

Description

Implement pricing support for Chooser options. Chooser options allow the holder to choose whether the option becomes a call or a put at a specified date before expiration.

Current State

• Chooser options return PricingError::UnsupportedOptionType
• No pricing model for choice flexibility

Target State

• Fully functional Chooser option pricing
• Support for simple and complex choosers
• Accurate pricing of the choice flexibility

Tasks

• Implement simple chooser options (same strike and expiration)
• Implement complex chooser options (different strikes/expirations)
• Implement Greeks calculations
• Add comprehensive tests
• Add documentation with examples

Technical Notes

Simple Chooser (Rubinstein 1991)

• Same strike K and expiration T for both call and put
• Choice date t < T

Alternative decomposition: Simple Chooser = Call(K, T) + Put(K, t) * e^(-(r-q)(T-t))

Estimated Effort

Medium (6-8 hours)