Convert search_select.js to TypeScript (issue #17)

- Add ts/search_select.ts: typed port of the SearchSelect/FilterSelect widget.
  Exports SearchSelectOption / SearchSelectChangeDetail as the single source of
  truth for the "search-select:change" event contract
- add_purchase.ts now imports those types via `import type` (no runtime
  coupling), instead of redefining them locally
- Declare window.readSearchSelect in ts/globals.d.ts
- Point the SearchSelect component Media and every view/e2e/test reference at
  the compiled dist/search_select.js
- Update doc comments in common/components/search_select.py to name the TS source

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

tests/test_node_tree.py

@@ -133,14 +133,14 @@ class RealComponentMediaTest(unittest.TestCase):
         from common.components import SearchSelect
 
         self.assertEqual(
-            collect_media(SearchSelect(name="games")).js, ("search_select.js",)
+            collect_media(SearchSelect(name="games")).js, ("dist/search_select.js",)
         )
 
     def test_filter_select_declares_its_script(self):
         from common.components import FilterSelect
 
         self.assertIn(
-            "search_select.js", collect_media(FilterSelect(field_name="type")).js
+            "dist/search_select.js", collect_media(FilterSelect(field_name="type")).js
         )
 
     def test_date_range_picker_declares_its_script(self):
@@ -170,7 +170,7 @@ class RealComponentMediaTest(unittest.TestCase):
 
         media = collect_media(FilterBar())
         self.assertIn("filter_bar.js", media.js)
-        self.assertIn("search_select.js", media.js)
+        self.assertIn("dist/search_select.js", media.js)
         self.assertIn("range_slider.js", media.js)