Clauses
We denote clauses as (cl <lit>*). The empty clause is therefore (cl).
Each literal is (<sign> <term>) with the sign being either + or -
(for a clause-level negation).
For example, (cl (- true) (+ (= b b))) represents the clause
\( \lnot \top \lor b=b \), or the sequent \( \top \vdash b=b \).