Function sv_cache_key 

pub fn sv_cache_key(ppnum_id: &str) -> String

Build the shared cache key for a given Human ppnum’s session_version.

Returned shape: sv:{ppnum_id}. Encapsulates the prefix so callers cannot accidentally mis-format the key (forgetting the colon, double prefixing, etc.). PAS writes this key on break-glass commit; PCS chat-auth and the pas-external SDK validator read it.

SSOT: STANDARDS_SHARED_CACHE §3.1 (sv: shared contract).