🐛 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,

lsp-server/test/test_tree_sitter/src/grammar.json

@@ -2457,24 +2457,42 @@
           "value": "for"
         },
         {
-          "type": "FIELD",
-          "name": "key",
-          "content": {
-            "type": "SYMBOL",
-            "name": "identifier"
-          }
-        },
-        {
-          "type": "STRING",
-          "value": ","
-        },
-        {
-          "type": "FIELD",
-          "name": "value",
-          "content": {
-            "type": "SYMBOL",
-            "name": "identifier"
-          }
+          "type": "CHOICE",
+          "members": [
+            {
+              "type": "SEQ",
+              "members": [
+                {
+                  "type": "FIELD",
+                  "name": "key",
+                  "content": {
+                    "type": "SYMBOL",
+                    "name": "identifier"
+                  }
+                },
+                {
+                  "type": "STRING",
+                  "value": ","
+                },
+                {
+                  "type": "FIELD",
+                  "name": "value",
+                  "content": {
+                    "type": "SYMBOL",
+                    "name": "identifier"
+                  }
+                }
+              ]
+            },
+            {
+              "type": "FIELD",
+              "name": "value",
+              "content": {
+                "type": "SYMBOL",
+                "name": "identifier"
+              }
+            }
+          ]
         },
         {
           "type": "ALIAS",