CRITICAL: get_agents() used SELECT * positional index 7 for status,
but column 7 is system_prompt (column 8 is status). Converted all
query functions in btmsg.rs and bttask.rs to named column access.
Fixed BtmsgAgent/BtmsgMessage TypeScript interfaces to use camelCase
matching Rust serde(rename_all = camelCase). Updated CommsTab consumer.