fix: emit valid XPath node test for ID elements in full-path mode

Address review feedback: In full-path XPath generation, elements with
IDs were producing bare predicates like `[@id='x']` which creates
invalid XPath steps like `//body/[@id='main']`. Now emits `*[@id='x']`
for full-path mode (e.g. `//body/*[@id='main']/*[@id='target']`).

Short-path XPath mode unchanged — still uses `//*[@id='x']` prefix.

Also added XPath evaluation assertion to the regression test to verify
the generated selector actually selects the correct element.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/parser/test_general.py

@@ -342,6 +342,11 @@ def test_full_path_selector_no_duplicate_ids():
     assert len(result) == 1
     assert result.first.text == "Hello"
 
+    # The generated XPath selector should also select the correct element
+    result = page.xpath(xpath_full)
+    assert len(result) == 1, f"XPath '{xpath_full}' selected {len(result)} elements, expected 1"
+    assert result.first.text == "Hello"
+
 
 def test_full_path_selector_mixed_id_and_no_id():
     """Test full path selectors with a mix of elements with and without ids"""