Two bugs in the add forms, both root-caused via the e2e harness:
1. add_game Name → Sort name never synced. syncSelectInputUntilChanged was
scoped to "form", but the first <form> on every page is the navbar logout
form — the add-form fields live in a later form, so the delegated listener
never heard their events. Scope to "#add-form" (the add-form wrapper). Also
switch the sync from the "change" event to "input" so Sort name mirrors Name
live as you type, not only on blur.
2. add_purchase Related game not disabled when Type == Game.
disableElementsWhenTrue set `.disabled` on #id_related_game, which is the
SearchSelect wrapper <div> (a <div> ignores `disabled`). Target the inner
[data-search-select-search] input instead, so the widget is actually disabled.
Adds two e2e regression tests (live sync; type-game disables the related-game
search input and re-enables it for other types).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>