feat: improve model config UI and move selector to chat input

- Move model selector from header to chat input (left of send button)
- Add per-model validation status (queued, running, valid, invalid)
- Filter model selector to only show verified models
- Add editable model IDs in config dialog
- Add custom model input field alongside suggested models dropdown
- Fix hover states on provider buttons and select triggers
- Update OpenAI suggested models with GPT-5 series
- Add alert-dialog component for delete confirmation

components/ui/command.tsx

@@ -145,18 +145,6 @@ function CommandItem({
         "data-[selected=true]:bg-accent data-[selected=true]:text-accent-foreground [&_svg:not([class*='text-'])]:text-muted-foreground relative flex cursor-default items-center gap-2 rounded-sm px-2 py-1.5 text-sm outline-hidden select-none data-[disabled=true]:pointer-events-none data-[disabled=true]:opacity-50 [&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4",
         className
       )}
-      onMouseEnter={(e) => {
-        // Ensure hover updates selection for visual feedback
-        const item = e.currentTarget
-        item.setAttribute("data-selected", "true")
-        // Deselect siblings
-        const siblings = item.parentElement?.querySelectorAll("[cmdk-item]")
-        siblings?.forEach((sibling) => {
-          if (sibling !== item) {
-            sibling.setAttribute("data-selected", "false")
-          }
-        })
-      }}
       {...props}
     />
   )