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>

common/components/custom_elements.py

@@ -146,6 +146,49 @@ register_element("selection-fields", "SelectionFields", SelectionFieldsProps)
 _SelectionFields = custom_element_builder("selection-fields")
 
 
+class RangeSliderProps(TypedDict):
+    min: int
+    max: int
+    step: int
+    mode: str  # "range" | "point"
+
+
+register_element("range-slider", "RangeSlider", RangeSliderProps)
+_RangeSlider = custom_element_builder("range-slider")
+
+
+class DateRangePickerProps(TypedDict):
+    pass
+
+
+register_element("date-range-picker", "DateRangePicker", DateRangePickerProps)
+_DateRangePicker = custom_element_builder("date-range-picker")
+
+
+class SearchSelectProps(TypedDict):
+    name: str
+    search_url: str
+    multi: bool
+    filter_mode: bool
+    free_text: bool
+    always_visible: bool
+    prefetch: int
+    sync_url: bool
+
+
+register_element("search-select", "SearchSelect", SearchSelectProps)
+_SearchSelect = custom_element_builder("search-select")
+
+
+class FilterBarProps(TypedDict):
+    preset_list_url: str
+    preset_save_url: str
+
+
+register_element("filter-bar", "FilterBar", FilterBarProps)
+_FilterBarElement = custom_element_builder("filter-bar")
+
+
 def SelectionFields(
     *,
     source: str,