coins.py keeps only Coin and the Palladium classes. The Bitcoin base class is folded into Palladium. COIN now defaults to Palladium. Tests and fixtures of the other coins are removed. test_blocks.py and test_transactions.py are simplified: one test each, fed by the palladium fixtures. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>