Svelte Guideline: Patterns — Button loading state with promise. Description: Auto-disable and show spinner while async operation is pending. Do: <Button loading={isSaving} onClickPromise={async () => await save()}>. Don't: Manual loading state tracking. Good Example: <Button loading={isSaving}>Save</Button>. Bad Example: <button disabled={isSaving}>{isSaving ? 'Saving...' : 'Save'}</button>. Severity: Medium. Docs: .