fix: prevent attachment button click from triggering form submit

The Paperclip (attach files) button in GlobalConfigControls is rendered
inside the prompt form without an explicit type attribute. Since the
default button type in a form is 'submit', clicking it triggers a form
submission in addition to opening the file dialog.

Add type="button" to prevent the implicit form submit.

Fixes #1428

Author: Br1an67

web/src/features/chat/global-config-controls.tsx

@@ -205,6 +205,7 @@ export function GlobalConfigControls({
       <Button
         variant="ghost"
         size="icon"
+        type="button"
         className="size-9 border-0"
         aria-label="Attach files"
         onClick={() => attachments.openFileDialog()}