Keep not-allowed cursor on disabled SearchSelect input

Excluding the inner search box from the global disabled rule also dropped its
cursor: not-allowed, so the pointer flickered between not-allowed (wrapper) and
the text I-beam (input) when moving across the disabled widget. Add
disabled:cursor-not-allowed to the search input so the cursor stays consistent.

e2e: assert the disabled inner input computes cursor: not-allowed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

e2e/test_widgets_e2e.py

@@ -178,6 +178,9 @@ def test_add_purchase_type_game_disables_related_game_search(
     # disabled-input surface) so the widget reads as one element, not a nested
     # box. transparent is mode-independent, so this holds in light and dark.
     assert search.evaluate("el => getComputedStyle(el).backgroundColor") == "rgba(0, 0, 0, 0)"
+    # The inner input carries the same not-allowed cursor as the wrapper, so the
+    # cursor doesn't flicker as the pointer crosses the widget.
+    assert search.evaluate("el => getComputedStyle(el).cursor") == "not-allowed"
 
     page.select_option("#id_type", "dlc")
     expect(search).to_be_enabled()