Switch safe string encoding from ~tilde codes to SOH-delimited codes throughout

YesNt.Interpreter.Tests/ListStatementsTests.cs

@@ -150,7 +150,7 @@ public class ListStatementsTests
         List<string> lines =
         [
             "list items new",
-            "list items add hello~spcworld",
+            "list items add \"hello world\"",
             "list items get 0",
             "var result = %out eval",
             "${result}"

YesNt.Interpreter.Tests/ProcessingStatementsTests.cs

@@ -46,9 +46,21 @@ public class ProcessingStatementsTests
     }
 
     [TestMethod]
-    public void EvalDecodesSafeStringTest()
+    public void EvalRawTildeSequenceIsLiteralTest()
     {
-        YesNtAssert.IsLineEqual("hello~nliworld eval", "hello\nworld");
+        YesNtAssert.IsLineEqual("hello~nliworld eval", "hello~nliworld");
+    }
+
+    [TestMethod]
+    public void EvalDecodesStringLiteralEscapesTest()
+    {
+        List<string> lines =
+        [
+            "var x = \"hello\\nworld\"",
+            "${x} eval"
+        ];
+
+        YesNtAssert.IsLastLineEqual(lines, "hello\nworld");
     }
 
     [TestMethod]