Drop altcoin pip extras, CI deps and docs; update CLAUDE.md and FORK.md

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

docs/features.rst

@@ -22,7 +22,7 @@ Features
   ElectrumX will failover round-robin style if the current one fails
   for any reason.
 - Peer discovery protocol removes need for IRC
-- Coin abstraction makes compatible altcoin and testnet support easy.
+- Coin abstraction makes testnet support easy.
 
 Implementation
 ==============