fix(encode): keep a []any of tables in the value-array form

Assisted-by: GLM 5.3

encode_test.go

@@ -597,6 +597,36 @@ func TestMarshalMixedArrayWithInlineTable(t *testing.T) {
 	}
 }
 
+// A []any of tables is what Parse produces for a value array of inline
+// tables; it must stay in the value-array form, or the output would re-parse
+// as []map[string]any and the round-trip would change the value's type.
+func TestMarshalValueArrayOfTablesStaysInline(t *testing.T) {
+	for _, doc := range []string{
+		"0=[{}]",
+		"a = [{x = 1}, {x = 2}]\n",
+		"b = [{x = 1}, 2, \"three\"]\n",
+	} {
+		tree, err := Parse([]byte(doc))
+		if err != nil {
+			t.Fatalf("%s: parse: %v", doc, err)
+		}
+		out, err := Marshal(tree)
+		if err != nil {
+			t.Fatalf("%s: marshal: %v", doc, err)
+		}
+		if bytes.HasPrefix(out, []byte("[[")) {
+			t.Errorf("%s: emitted the [[header]] form for a value array:\n%s", doc, out)
+		}
+		re, err := Parse(out)
+		if err != nil {
+			t.Fatalf("%s: re-parse: %v\ndoc:\n%s", doc, err, out)
+		}
+		if !tomlEqual(tree, re) {
+			t.Errorf("%s: round-trip changed the tree:\nwas: %#v\nnow: %#v\ndoc:\n%s", doc, tree, re, out)
+		}
+	}
+}
+
 func TestMarshalNestedInlineTables(t *testing.T) {
 	tree := map[string]any{
 		"mix": []any{