Convert onSwap widgets to custom elements (issue #18)

Replaces the four onSwap-based widgets with TypeScript custom elements
following the pattern from PR #16. Each widget gets a class extending
HTMLElement with connectedCallback/disconnectedCallback, typed props via
register_element + gen_element_types codegen, and lives in ts/elements/.

- range-slider: RangeSliderElement; Python uses _RangeSlider builder
- date-range-picker: DateRangePickerElement; Python uses _DateRangePicker builder
- search-select: SearchSelectElement; Python uses _SearchSelect builder;
  data-* attrs become plain attrs (data-name -> name, data-search-url -> search-url, etc.)
- filter-bar: FilterBarElement; props carry preset URLs; onclick/onsubmit
  attrs replaced with data-filter-bar-* sentinel attrs; all window.* globals removed

Deletes ts/range_slider.ts, ts/search_select.ts, ts/date_range_picker.ts,
ts/filter_bar.ts. Updates all tests and e2e pages to use the new element
selectors and script paths (dist/elements/<tag>.js).

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

tests/test_node_tree.py

@@ -133,14 +133,16 @@ class RealComponentMediaTest(unittest.TestCase):
         from common.components import SearchSelect
 
         self.assertEqual(
-            collect_media(SearchSelect(name="games")).js, ("dist/search_select.js",)
+            collect_media(SearchSelect(name="games")).js,
+            ("dist/elements/search-select.js",),
         )
 
     def test_filter_select_declares_its_script(self):
         from common.components import FilterSelect
 
         self.assertIn(
-            "dist/search_select.js", collect_media(FilterSelect(field_name="type")).js
+            "dist/elements/search-select.js",
+            collect_media(FilterSelect(field_name="type")).js,
         )
 
     def test_date_range_picker_declares_its_script(self):
@@ -149,7 +151,7 @@ class RealComponentMediaTest(unittest.TestCase):
         media = collect_media(
             DateRangePicker(label="Played", input_name_prefix="played")
         )
-        self.assertEqual(media.js, ("dist/date_range_picker.js",))
+        self.assertEqual(media.js, ("dist/elements/date-range-picker.js",))
 
     def test_range_slider_declares_its_script(self):
         from common.components.filters import RangeSlider
@@ -159,7 +161,7 @@ class RealComponentMediaTest(unittest.TestCase):
                 label="Year", input_name_prefix="year", range_min=2000, range_max=2025
             )
         )
-        self.assertEqual(media.js, ("dist/range_slider.js",))
+        self.assertEqual(media.js, ("dist/elements/range-slider.js",))
 
     def test_filter_bar_collects_chrome_and_widget_media(self):
         """A FilterBar's media merges its own chrome script with the scripts that
@@ -169,9 +171,9 @@ class RealComponentMediaTest(unittest.TestCase):
         from common.components import FilterBar
 
         media = collect_media(FilterBar())
-        self.assertIn("dist/filter_bar.js", media.js)
-        self.assertIn("dist/search_select.js", media.js)
-        self.assertIn("dist/range_slider.js", media.js)
+        self.assertIn("dist/elements/filter-bar.js", media.js)
+        self.assertIn("dist/elements/search-select.js", media.js)
+        self.assertIn("dist/elements/range-slider.js", media.js)
 
 
 class HtpyStyleSugarTest(unittest.TestCase):