ground_notcoexistence instantiates NotCoExistence with the same operand twice

Open nl2ltl/engines/grounding.py and inspect ground_notcoexistence. Run the reported _get_formulas reproduction with the two connectors, then correct the duplicated operand so the result is (NotCoExistence reject_request escalate_to_human). Done means the grounding preserves both connector names instead of producing a self-pair.

Bug

nl2ltl/engines/grounding.py:

def ground_notcoexistence(connectors: Dict[str, float]) -> Set[Template]:
    if len(list(connectors)) >= 2:
        return {
            NotCoExistence(
                Atomic(decapitalize(list(connectors)[1])),
                Atomic(decapitalize(list(connectors)[1])),   # <-- [1] twice
            )
        }

Both operands are built from list(connectors)[1], so any two-symbol grounding produces a degenerate self-pair. Reproduction:

>>> from nl2ltl.engines.utils import _get_formulas
>>> _get_formulas("notcoexistence", {"reject_request": 1.0, "escalate_to_human": 1.0})
{(NotCoExistence escalate_to_human escalate_to_human)}

Expected: (NotCoExistence reject_request escalate_to_human).

The resulting LTLf, F(x) -> ~F(x), is equivalent to G(!x) — "x never happens" — which silently changes the meaning of the translated requirement (we caught it because a round-trip paraphrase of the formula no longer matched the input sentence).

Fix

Atomic(decapitalize(list(connectors)[0])),
Atomic(decapitalize(list(connectors)[1])),

Observed on nl2ltl from PyPI (Python 3.13). Found while building a Claude-backed custom Engine for translating agent-guardrail policies to DECLARE. Can send a PR if useful.