feat: honour TextMarshaler and TextUnmarshaler by default

Assisted-by: DeepSeek V4.1 Flash

CHANGELOG.md

@@ -9,7 +9,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
--
+- `encoding.TextMarshaler` and `encoding.TextUnmarshaler` are honoured by
+  default, with no option to switch them off. A type that implements them is
+  encoded as a TOML string and decoded from one: `net.IP` becomes
+  `"192.0.2.1"`, and a user type with `MarshalText` or `UnmarshalText` follows.
+  `MarshalTOML` and `UnmarshalTOML` still win over the text methods, and the
+  four date-time types keep their bare timestamp form instead of becoming a
+  quoted string. A struct type that implements the interface now encodes as a
+  string where it was a table before, which is the breaking part of the change.
+- `time.Duration` is encoded in its canonical Go form as a TOML string,
+  `1h30m0s`, because TOML has no duration type; the decoder reads that string
+  back and still accepts a bare integer as the nanosecond count.
 
 ### Changed