fix: use native page xpath api for xpath selectors (#853)

## ℹ️ Description
*Provide a concise summary of the changes introduced in this pull
request.*

- Link to the related issue(s): n/a
- Describe the motivation and context for this change.
This replaces the stacked XPath work from #845 with a standalone fix
from `main`. It makes `By.XPATH` use the native page XPath API instead
of routing XPath selectors through text lookup.

## 📋 Changes Summary

- Add private XPath helpers in `WebScrapingMixin` for first-match and
all-match lookups.
- Route `By.XPATH` in `_web_find_once()` and `_web_find_all_once()`
through `page.xpath(...)`.
- Add unit coverage for XPath helper behavior, empty results, and
unsupported parent scoping.
- No configuration changes or new dependencies.

### ⚙️ Type of Change
Select the type(s) of change(s) included in this pull request:
- [x] 🐞 Bug fix (non-breaking change which fixes an issue)
- [ ] ✨ New feature (adds new functionality without breaking existing
usage)
- [ ] 💥 Breaking change (changes that might break existing user setups,
scripts, or configurations)


## ✅ Checklist
Before requesting a review, confirm the following:
- [x] I have reviewed my changes to ensure they meet the project's
standards.
- [x] I have tested my changes and ensured that all tests pass (`pdm run
test`).
- [x] I have formatted the code (`pdm run format`).
- [x] I have verified that linting passes (`pdm run lint`).
- [x] I have updated documentation where necessary.

By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice.


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Refactoring**
* Improved web scraping element selection reliability through
streamlined XPath operations and better internal helper methods.

* **Tests**
* Added comprehensive unit tests for XPath-based element lookup
operations to ensure consistent behavior.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

tests/unit/test_web_scraping_mixin.py

@@ -666,6 +666,51 @@ class TestSelectorTimeoutMessages:
         assert expected_message == call.kwargs["timeout_error_message"]
         assert call.kwargs["apply_multiplier"] is False
 
+    @pytest.mark.asyncio
+    async def test_web_find_once_xpath_uses_xpath_api(self, web_scraper:WebScrapingMixin, mock_page:TrulyAwaitableMockPage) -> None:
+        """By.XPATH should use the native page.xpath API and return first non-null match."""
+        xpath_match = MagicMock(spec = Element)
+        mock_page.xpath = AsyncMock(return_value = [None, xpath_match])
+
+        result = await web_scraper._web_find_once(By.XPATH, "//div[@id='hero']", 0.2)
+
+        assert result is xpath_match
+        mock_page.xpath.assert_awaited_once_with("//div[@id='hero']", timeout = 0)
+
+    @pytest.mark.asyncio
+    async def test_web_find_once_xpath_returns_none_when_no_matches(self, web_scraper:WebScrapingMixin, mock_page:TrulyAwaitableMockPage) -> None:
+        """_xpath_first should return None when xpath yields no usable match."""
+        mock_page.xpath = AsyncMock(return_value = [None, None])
+
+        result = await web_scraper._xpath_first("//missing")
+
+        assert result is None
+        mock_page.xpath.assert_awaited_once_with("//missing", timeout = 0)
+
+    @pytest.mark.asyncio
+    async def test_web_find_all_once_xpath_uses_xpath_api(self, web_scraper:WebScrapingMixin, mock_page:TrulyAwaitableMockPage) -> None:
+        """By.XPATH should use page.xpath and return all non-null matches."""
+        first_match = MagicMock(spec = Element)
+        second_match = MagicMock(spec = Element)
+        mock_page.xpath = AsyncMock(return_value = [first_match, None, second_match])
+
+        result = await web_scraper._web_find_all_once(By.XPATH, "//footer", 0.2)
+
+        assert result == [first_match, second_match]
+        mock_page.xpath.assert_awaited_once_with("//footer", timeout = 0)
+
+    @pytest.mark.asyncio
+    async def test_web_find_once_xpath_rejects_parent(self, web_scraper:WebScrapingMixin) -> None:
+        """XPath lookups currently do not support parent-scoped queries."""
+        with pytest.raises(AssertionError, match = "Specifying a parent element currently not supported"):
+            await web_scraper._web_find_once(By.XPATH, "//div", 0.1, parent = AsyncMock(spec = Element))
+
+    @pytest.mark.asyncio
+    async def test_web_find_all_once_xpath_rejects_parent(self, web_scraper:WebScrapingMixin) -> None:
+        """XPath multi-lookups currently do not support parent-scoped queries."""
+        with pytest.raises(AssertionError, match = "Specifying a parent element currently not supported"):
+            await web_scraper._web_find_all_once(By.XPATH, "//div", 0.1, parent = AsyncMock(spec = Element))
+
     @pytest.mark.asyncio
     @pytest.mark.parametrize(
         ("selector_type", "selector_value", "expected_message"),