Implement Arena of Antiquity, Fragrant Forest stadiums and Lucky Egg tool

[bcollazo]

Summary

This PR adds implementations for three card effects: two stadium cards (Arena of Antiquity and Fragrant Forest) and one tool card (Lucky Egg), along with comprehensive test coverage for each.

Key Changes

Stadium Effects

• Arena of Antiquity: Adds +20 damage bonus when Fighting-type Pokémon attack the opponent's Active Pokémon ex. Implemented in stadiums.rs with damage calculation integrated into the core damage modification logic in hooks/core.rs.
• Fragrant Forest: Allows each player to put a random Basic Grass Pokémon from their deck into their hand once per turn. Implemented with proper action forecasting and probability handling for multiple Basic Grass Pokémon in deck.

Tool Effect

• Lucky Egg: When a Pokémon with Lucky Egg attached is knocked out by an opponent's active attack, the player draws cards until their hand has 5 cards. Integrated into the knockout handler in hooks/core.rs with proper opponent attack detection.

Implementation Details

• Stadium effects are registered in is_stadium_effect_implemented() for validation
• Fragrant Forest uses the existing forecast_use_stadium() mechanism with probability-based outcomes for random selection
• Lucky Egg leverages the existing on_knockout() hook, requiring the attacking_ref parameter to distinguish opponent attacks from other damage sources
• All three cards include proper action generation checks to prevent invalid moves (e.g., UseStadium when no Basic Grass Pokémon available)

Testing

• Added 4 comprehensive tests for Fragrant Forest covering availability, card drawing, and per-turn usage limits
• Added 3 tests for Arena of Antiquity covering Fighting vs ex bonus, non-ex immunity, and non-Fighting immunity
• Added 2 tests for Lucky Egg covering KO draw trigger and non-attack damage immunity
• Updated test module registrations in tests/stadiums.rs and tests/tools.rs

Minor Fixes

• Removed unnecessary mut qualifiers in several test functions for cleaner code

https://claude.ai/code/session_0166D44Pws5WCDu5xnTDD7h2