Document `form().pending` in the remote functions

Describe the problem

Until now, form submission pending state required customizing the use:enhance as documented in this tutorial.

I've personally created a svelte-form-enhanced library just to handle this issue.

This can now be achieved with form().pending, but is only mentioned in the multiple instances of a form section.

{#each await getTodos() as todo}
  {@const modify = modifyTodo.for(todo.id)}
  <form {...modify}>
    <!-- -->
    <button disabled={!!modify.pending}>save changes</button>
  </form>
{/each}

Describe the proposed solution

I hope it is documented as an independent section.

• Disable form when there is a pending submission (avoid double click, double submission in the client)
• Show saving state as in the existing tutorial.

<script lang="ts">
  import { addId } from './ids.remote';
</script>

<form {...addId}>
  <fieldset disabled={!!addId.pending}>
    <!-- form content goes here -->
  </fieldset>
</form>

Alternatives considered

No response

Importance

nice to have

Additional Information

No response

Start in the remote functions documentation at the existing “Multiple instances of a form” section and compare its form().pending example with the linked customizing use:enhance tutorial. Add an independent explanation covering pending submissions, disabled controls, and saving feedback; done means the remote functions docs clearly show these use cases.