Function find_by_hash 

pub fn find_by_hash(
    conn: &Connection,
    namespace: &str,
    body_hash: &str,
) -> Result<Option<i64>, AppError>

Looks up a live memory by exact body_hash within a namespace.

Used during remember to short-circuit semantic duplicates before spending an embedding call.

Returns

Ok(Some(id)) when a live memory with the same hash exists, Ok(None) otherwise.

Errors

Returns Err(AppError::Database) on any rusqlite failure.