Handles FerricStore-native commands that go beyond the Redis command set.

Supported commands

• CAS key expected new [EX seconds] -- compare-and-swap
• LOCK key owner ttl_ms -- acquire a distributed lock
• UNLOCK key owner -- release a distributed lock
• EXTEND key owner ttl_ms -- extend lock TTL
• RATELIMIT.ADD key window_ms max [count] -- sliding window rate limiter
• KEY_INFO key -- returns diagnostic metadata about a key