feat(ai): keep provider headers visible

apps/desktop/src/components/editor/AiAssistant.vue

@@ -2934,8 +2934,8 @@ async function openExternalUrl(url: string) {
                     <input v-model="modelSearchQuery" type="text" :placeholder="t('ai.searchModels')" class="w-full rounded-sm border bg-background py-1.5 pl-7 pr-2 text-xs outline-none focus:ring-1 focus:ring-primary" @click.stop />
                   </div>
                   <div class="max-h-80 overflow-auto">
-                    <template v-for="(config, configIndex) in configuredProviders" :key="config.id">
-                      <button type="button" class="flex w-full items-center gap-2 rounded-sm px-2 py-1.5 text-left text-xs text-foreground hover:bg-muted" :aria-expanded="!isModelConfigCollapsed(config.id)" @click="toggleModelConfig(config.id)">
+                    <div v-for="(config, configIndex) in configuredProviders" :key="config.id" class="relative">
+                      <button type="button" class="sticky top-0 z-10 flex w-full items-center gap-2 rounded-sm bg-popover px-2 py-1.5 text-left text-xs text-foreground hover:bg-muted" :aria-expanded="!isModelConfigCollapsed(config.id)" @click="toggleModelConfig(config.id)">
                         <ChevronRight class="h-3.5 w-3.5 shrink-0 transition-transform" :class="{ 'rotate-90': !isModelConfigCollapsed(config.id) }" />
                         <AiProviderLogo :provider="config.provider" :label="AI_PROVIDER_PRESETS[config.provider]?.label ?? config.provider" :icon-slug="AI_PROVIDER_PRESETS[config.provider]?.iconSlug" class="h-3.5 w-3.5 shrink-0" />
                         <span class="min-w-0 flex-1 truncate font-medium">{{ config.name }}</span>
@@ -2984,7 +2984,7 @@ async function openExternalUrl(url: string) {
                         </button>
                       </div>
                       <div v-if="configIndex < configuredProviders.length - 1" class="my-1 border-t" />
-                    </template>
+                    </div>
                   </div>
                   <div v-if="settings.activeModel" class="border-t pt-1">
                     <Popover v-model:open="effortMenuOpen">