fix: encode mixed arrays with inline table elements

Assisted-by: GLM 5.3 Flash

docs/API.md

@@ -289,6 +289,18 @@ func (p Port) MarshalTOML() (any, error) {
 }
 ```
 
+### Arrays
+
+An array whose every element is a table (`[]struct`, `[]map[string]V`, after
+pointer dereference) emits as an array of tables. TOML also lets one array mix
+tables with scalars; such an array emits as a plain value array, with the
+table elements rendered as inline tables:
+
+```go
+tree, _ := interpres.Parse([]byte(`arr = [1, {a = 2}, "x"]`))
+out, _ := interpres.Marshal(tree) // arr = [1, {a = 2}, "x"]
+```
+
 ### Empty arrays
 
 A nil slice is always omitted. An empty (length 0) array of tables is always