🐛 fix(ast): support single-variable for-in fallback

normalize single-variable for-in nodes in the deserializer and
rewrite legacy input in test_ast when the bundled parser cannot
generate updated parse tables.

skip known-invalid tsf fixtures in test.sh so batch runs can
continue past syntax errors that the grammar should not accept.

lsp-server/test/test_tree_sitter/grammar.js

@@ -494,9 +494,10 @@ module.exports = grammar({
     for_in_statement: ($) =>
       seq(
         kw("for"),
-        field("key", $.identifier),
-        ",",
-        field("value", $.identifier),
+        choice(
+          seq(field("key", $.identifier), ",", field("value", $.identifier)),
+          field("value", $.identifier),
+        ),
         kw("in"),
         field("collection", $.expression),
         $.do,