app: number fields no longer throw "e.preventDefault is not a function" (#735)

`useForm`'s input handlers called `e.preventDefault()` unconditionally, but the
Mantine-backed `NumberField` (Sleep between requests, Depth, Maximum Pages)
hands them a bare `{target}` object because NumberInput emits a value, not an
event.  Every keystroke in those fields threw.

`handleInputEvent` now only calls `preventDefault` when the argument actually
has one, and `getInputProps`' wrapper no longer repeats the call.  Audited every
other `preventDefault` call site: all are bound to real DOM/React events or a
guarded no-argument call.

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

app/src/components/Download.test.js

@@ -1,8 +1,9 @@
 import React from 'react';
 import {render, screen, waitFor} from '@testing-library/react';
 import userEvent from '@testing-library/user-event';
-import {DestinationForm} from './Download';
-import {createTestForm} from '../test-utils';
+import {DepthInputForm, DestinationForm} from './Download';
+import {useForm} from '../hooks/useForm';
+import {createTestForm, renderWithProviders} from '../test-utils';
 
 // Mock DirectorySearch component - simplified to avoid useState/useEffect warnings
 jest.mock('./Common', () => {
@@ -251,3 +252,26 @@ describe('DestinationForm', () => {
         });
     });
 });
+
+describe('NumberField', () => {
+    // Renders a NumberField against a real useForm: the Mantine NumberInput passes a value (not an
+    // event) to onChange, which used to reach `e.preventDefault()` and throw while typing.
+    function DepthHarness({onData}) {
+        const form = useForm({defaultFormData: {settings: {depth: ''}}, submitter: jest.fn()});
+        onData(form.formData);
+        return <DepthInputForm form={form}/>;
+    }
+
+    it('typing into a NumberField updates the form without throwing', async () => {
+        let latest = null;
+        renderWithProviders(<DepthHarness onData={(d) => latest = d}/>);
+
+        const input = screen.getByRole('textbox', {name: /Depth/});
+        await userEvent.type(input, '3');
+
+        await waitFor(() => {
+            expect(latest.settings.depth).toBe(3);
+        });
+        expect(input).toHaveValue('3');
+    });
+});

app/src/hooks/useForm.js

@@ -188,7 +188,9 @@ export function useForm({
     }, 300), [validators]);
 
     const handleInputEvent = (e) => {
-        if (e) e.preventDefault();
+        // Mantine inputs (NumberInput, etc.) hand back a value rather than a DOM event, so callers
+        // wrap it as a bare `{target: {...}}` object.  Only a real event has `preventDefault`.
+        if (e && typeof e.preventDefault === 'function') e.preventDefault();
         let {type, value} = e.target;
         let {path} = e.target.dataset;
         path = path || e.target.name;
@@ -286,7 +288,8 @@ export function useForm({
         const [customProps, inputAttrs] = getCustomProps({name, validator, path, type, required, afterChange});
 
         const localHandleInputEvent = async (e) => {
-            if (e) e.preventDefault();
+            // `handleInputEvent` already handles a real event's preventDefault, and tolerates the
+            // value-shaped objects Mantine-backed fields pass.
             const value = handleInputEvent(e);
             if (onChange) {
                 await onChange(value);

app/src/hooks/useForm.test.js

@@ -465,6 +465,39 @@ describe('useForm', () => {
             expect(result.current.formData.sleep_requests).toBe(0.75);
         });
 
+        it('handleInputEvent accepts a value-shaped event with no preventDefault (Mantine NumberInput)', () => {
+            // Mantine's NumberInput hands back the value, so NumberField wraps it in a bare
+            // {target} object.  Typing must not throw "e.preventDefault is not a function".
+            const {result} = renderHook(() => useForm({
+                defaultFormData: {settings: {sleep_requests: ''}},
+                submitter: jest.fn(),
+            }));
+
+            act(() => {
+                result.current.handleInputEvent({
+                    target: {type: 'number', value: 0.75, dataset: {path: 'settings.sleep_requests'}},
+                });
+            });
+
+            expect(result.current.formData.settings.sleep_requests).toBe(0.75);
+        });
+
+        it('getInputProps onChange accepts a value-shaped event with no preventDefault', async () => {
+            const {result} = renderHook(() => useForm({
+                defaultFormData: {settings: {depth: ''}},
+                submitter: jest.fn(),
+            }));
+
+            await act(async () => {
+                const [inputProps] = result.current.getInputProps({name: 'depth', path: 'settings.depth', type: 'number'});
+                await inputProps.onChange({
+                    target: {type: 'number', value: 3, dataset: {path: 'settings.depth'}},
+                });
+            });
+
+            expect(result.current.formData.settings.depth).toBe(3);
+        });
+
         it('handleInputEvent uses data-path attribute when available', () => {
             const {result} = renderHook(() => useForm({
                 defaultFormData: {nested: {field: ''}},