postgres.js unsafe() with $n::jsonb param double-encodes a JSON.stringify'd string

With postgres.js sql.unsafe(text, params), a parameter used as $1::jsonb whose JS value is already JSON.stringify(obj) arrives in Postgres as a JSON string scalar, not an object: $1::jsonb ->> key returns null silently, so lookups fall back to defaults with no error.

Pass the plain JS object (not a string) when the server infers the parameter type as json/jsonb: postgres.js serializes it once with its JSON serializer. Only pre-stringify when the parameter is typed text. Add a test proving the jsonb value is actually read (for example a per-key limit taking effect), since the bug fails silently.