test(syntax): update error assertions to Peggy-native format

Parse errors now emit Peggy's diagnostic format:

  Unclosed element `div`
   --> route.hbs:1:1
    |
  1 | <div>
    | ^^^^^

Two changes:

1. test-utils/syntax-error.ts — adds `parseErrorFor(msg, source, module,
   line, col, spanLength?)` which replicates Peggy's format() output from
   the full source text + span position. Keeps `syntaxErrorFor(msg, code,
   module, line, col)` producing `formatSyntaxError` output for the
   semantic compiler errors in integration tests.

2. parser-node-test.ts — migrates all 20 syntaxErrorFor() calls to
   parseErrorFor(), passing the full template source and the correct span
   length derived by running the parser. The integration tests that test
   semantic errors (strict-mode-test.ts, dynamic-modifiers-test.ts)
   continue to use syntaxErrorFor unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

Author: NullVoxPopuli

packages/@glimmer-workspace/test-utils/lib/syntax-error.ts

@@ -1,5 +1,63 @@
 import { formatSyntaxError } from '@glimmer/syntax';
 
+/**
+ * Build an expected error for parse errors thrown by the Peggy grammar.
+ * Produces the Peggy-native diagnostic format:
+ *
+ *   {message}
+ *    --> {module}:{line}:{col}
+ *     |
+ *   {line} | {full source line}
+ *     |    ^^^^
+ *
+ * Parameters:
+ *   source     – the full template source text (the same string passed to parse()).
+ *   line       – 1-based line number.
+ *   column     – 0-based column (SourceSpan.loc.start.column).
+ *   spanLength – number of '^' carets. Defaults to 1.
+ */
+export function parseErrorFor(
+  message: string,
+  source: string,
+  moduleName: string,
+  line: number,
+  column: number,
+  spanLength = 1
+): Error {
+  const peggyCol = column + 1;
+  const loc = `${moduleName}:${line}:${peggyCol}`;
+
+  let formatted: string;
+  if (source) {
+    const srcLines = source.split(/\r\n|\n|\r/g);
+    const sourceLine = srcLines[line - 1] ?? '';
+    const filler = ''.padEnd(String(line).length, ' ');
+    const hatLen = spanLength || 1;
+    formatted =
+      `${message}\n --> ${loc}\n` +
+      `${filler} |\n` +
+      `${line} | ${sourceLine}\n` +
+      `${filler} | ${''.padEnd(column, ' ')}${''.padEnd(hatLen, '^')}`;
+  } else {
+    formatted = `${message}\n at ${loc}`;
+  }
+
+  const error = new Error(formatted);
+  error.name = 'SyntaxError';
+  return error;
+}
+
+/**
+ * Build an expected error for semantic compiler errors thrown via generateSyntaxError.
+ * Produces the formatSyntaxError format (used outside of Peggy parse errors).
+ *
+ *   {message}
+ *
+ *      {line} | {code snippet}
+ *             | ^^^^^^^^^^^^^
+ *
+ *        at {module}:{line}:{col}
+ */
 export function syntaxErrorFor(
   message: string,
   code: string,