Enforce SQL-backed count responses in the agent and allow NCID voter lookups

[copelco]

Updates the agent prompt rules to improve response accuracy and safety behavior for voter-data questions. The main changes:

1. Clarify that NCID is a public identifier (not PII), allow NCID-filtered queries, and explicitly allow voter event history lookups by NCID.
2. Require fresh run_sql_query calls for every reported count/total, preventing reuse of numbers from prior conversation context.
3. Keep active-voter filtering as default, but exempt NCID-specific voter event history queries from that default filter.