fix bugs

1. "first keyword: --"  cosmetic bug
2. re error

skills/pyspark-sql-guardrails/scripts/test_sql_guard.py

@@ -44,6 +44,9 @@ expect_ok("trailing semicolon",  "SELECT 1 FROM dual;")
 expect_ok("leading -- comment",  "-- comment\nSELECT 1")
 expect_ok("leading /* comment",  "/* hi */ SELECT 1")
 expect_ok("INSERT ... SELECT",   "INSERT INTO t SELECT 1")
+expect_ok("string 'drop'",       "SELECT 'drop' AS note FROM dual")
+expect_ok("quoted identifier",   'SELECT "drop" AS note FROM dual')
+expect_ok("escaped quote",       "SELECT 'don''t drop' AS note FROM dual")
 
 print()
 print("=== EXPECT_RAISE ===")