Keep BASIC fixtures within the input line limit

Reflow the approved reference cases, shorten local fixture comments, and split the executable docs line so the 80-byte input buffer can read every source line.

Co-authored-by: andrew <andrew@aklabs.net>

tests/language/functions/mod.bas

@@ -1,6 +1,6 @@
 10 PRINT MOD(10, 3)
 20 PRINT MOD(12, 5)
 30 PRINT MOD(4, 2)
-40 REM MOD() ONLY WORKS WITH INTEGERS - RESULTS WITH FLOATING POINT ARE UNRELIABLE
+40 REM MOD() ONLY WORKS WITH INTEGERS - FLOATING-POINT RESULTS ARE UNRELIABLE
 50 REM PRINT MOD(1.2, 0.4)
 60 REM THERE IS NO ERROR THROWN HERE. JUST DONT DO IT.