fix(encode): fall back from the literal multiline form when unsafe

Assisted-by: GLM 5.3

CHANGELOG.md

@@ -50,6 +50,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   and nested arrays of tables: `[[a]]`, `b.c = 1`, `[[a]]`, `[a.b]` parses, as
   the TOML examples in the spec shape it. The records of the previous element
   falsely rejected the same paths in the next one.
+- `UseLiteralMultiline` falls back to the escaped basic string when the value
+  cannot be carried verbatim by the literal form: a run of three single quotes,
+  a control character, or a lone carriage return. Such values previously
+  produced output that did not re-parse.
 - A float with an exponent marker but no digits (`1e`, `0.0E`) is rejected;
   the exponent requires at least one digit.
 - A date-time offset outside 00:00 through 23:59 is rejected; such offsets