Checkbox atom: new FA wrapper with brand theming

- New Checkbox atom wrapping MUI Checkbox (forwardRef, displayName)
- MuiCheckbox theme overrides: warm gold checked, focus ring, disabled muted
- Stories: Default, States, TermsAgreement, Checklist
- PaymentStep: now imports Checkbox from atom instead of MUI directly

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/atoms/Checkbox/Checkbox.stories.tsx

@@ -0,0 +1,144 @@
+import { useState } from 'react';
+import type { Meta, StoryObj } from '@storybook/react';
+import { Checkbox } from './Checkbox';
+import { Typography } from '../Typography';
+import Box from '@mui/material/Box';
+import FormControlLabel from '@mui/material/FormControlLabel';
+import FormGroup from '@mui/material/FormGroup';
+
+const meta: Meta<typeof Checkbox> = {
+  title: 'Atoms/Checkbox',
+  component: Checkbox,
+  tags: ['autodocs'],
+  parameters: {
+    layout: 'centered',
+  },
+  argTypes: {
+    checked: {
+      control: 'boolean',
+      description: 'Whether the checkbox is checked',
+    },
+    disabled: {
+      control: 'boolean',
+      description: 'Disable the checkbox',
+      table: { defaultValue: { summary: 'false' } },
+    },
+  },
+};
+
+export default meta;
+type Story = StoryObj<typeof Checkbox>;
+
+// ─── Default ────────────────────────────────────────────────────────────────
+
+/** Default checkbox — unchecked */
+export const Default: Story = {
+  args: {},
+};
+
+// ─── States ─────────────────────────────────────────────────────────────────
+
+/** All visual states */
+export const States: Story = {
+  render: () => (
+    <Box sx={{ display: 'flex', flexDirection: 'column', gap: 1 }}>
+      <FormControlLabel control={<Checkbox />} label="Unchecked" />
+      <FormControlLabel control={<Checkbox defaultChecked />} label="Checked" />
+      <FormControlLabel control={<Checkbox disabled />} label="Disabled unchecked" />
+      <FormControlLabel control={<Checkbox disabled defaultChecked />} label="Disabled checked" />
+      <FormControlLabel control={<Checkbox indeterminate />} label="Indeterminate" />
+    </Box>
+  ),
+};
+
+// ─── Terms Agreement ────────────────────────────────────────────────────────
+
+/**
+ * Realistic pattern — terms and conditions checkbox in a payment form.
+ */
+export const TermsAgreement: Story = {
+  name: 'Terms Agreement',
+  render: () => {
+    const TermsDemo = () => {
+      const [accepted, setAccepted] = useState(false);
+
+      return (
+        <Box sx={{ maxWidth: 420 }}>
+          <FormControlLabel
+            control={
+              <Checkbox checked={accepted} onChange={(e) => setAccepted(e.target.checked)} />
+            }
+            label={
+              <Typography variant="body2">
+                I agree to the service agreement and privacy policy
+              </Typography>
+            }
+            sx={{ alignItems: 'flex-start', '& .MuiCheckbox-root': { pt: 0.5 } }}
+          />
+          {!accepted && (
+            <Typography
+              variant="body2"
+              sx={{ ml: 4, mt: 0.5, color: 'var(--fa-color-text-brand)' }}
+            >
+              You must accept the terms to continue
+            </Typography>
+          )}
+        </Box>
+      );
+    };
+
+    return <TermsDemo />;
+  },
+};
+
+// ─── Checklist ──────────────────────────────────────────────────────────────
+
+/**
+ * Checklist pattern — multiple independent options.
+ */
+export const Checklist: Story = {
+  render: () => {
+    const ChecklistDemo = () => {
+      const [items, setItems] = useState({
+        dressing: true,
+        viewing: false,
+        prayers: false,
+        announcement: true,
+      });
+
+      const toggle = (key: keyof typeof items) => {
+        setItems((prev) => ({ ...prev, [key]: !prev[key] }));
+      };
+
+      return (
+        <Box sx={{ maxWidth: 420 }}>
+          <Typography variant="h5" sx={{ mb: 2 }}>
+            Complimentary inclusions
+          </Typography>
+          <FormGroup>
+            <FormControlLabel
+              control={<Checkbox checked={items.dressing} onChange={() => toggle('dressing')} />}
+              label="Dressing and preparation"
+            />
+            <FormControlLabel
+              control={<Checkbox checked={items.viewing} onChange={() => toggle('viewing')} />}
+              label="Viewing for family and friends"
+            />
+            <FormControlLabel
+              control={<Checkbox checked={items.prayers} onChange={() => toggle('prayers')} />}
+              label="Prayers or vigil"
+            />
+            <FormControlLabel
+              control={
+                <Checkbox checked={items.announcement} onChange={() => toggle('announcement')} />
+              }
+              label="Funeral announcement"
+            />
+          </FormGroup>
+        </Box>
+      );
+    };
+
+    return <ChecklistDemo />;
+  },
+};

src/components/atoms/Checkbox/Checkbox.tsx

@@ -0,0 +1,35 @@
+import React from 'react';
+import MuiCheckbox from '@mui/material/Checkbox';
+import type { CheckboxProps as MuiCheckboxProps } from '@mui/material/Checkbox';
+
+// ─── Types ───────────────────────────────────────────────────────────────────
+
+/** Props for the FA Checkbox component */
+export type CheckboxProps = MuiCheckboxProps;
+
+// ─── Component ───────────────────────────────────────────────────────────────
+
+/**
+ * Checkbox for the FA design system.
+ *
+ * Multi-select control for independent boolean options. Wraps MUI Checkbox
+ * with FA brand tokens — warm gold fill when checked, rounded square shape.
+ *
+ * Usage:
+ * - For independent booleans ("I agree to terms", "Include catering")
+ * - For mutually exclusive options, use Radio instead
+ * - For binary toggles, use Switch instead
+ *
+ * **Accessibility**: Always wrap in `FormControlLabel` with a `label` prop.
+ * A standalone Checkbox without a visible label is inaccessible — screen
+ * readers cannot announce what the checkbox controls.
+ * ```tsx
+ * <FormControlLabel control={<Checkbox />} label="I agree to the terms" />
+ * ```
+ */
+export const Checkbox = React.forwardRef<HTMLButtonElement, CheckboxProps>((props, ref) => {
+  return <MuiCheckbox ref={ref} {...props} />;
+});
+
+Checkbox.displayName = 'Checkbox';
+export default Checkbox;

src/components/atoms/Checkbox/index.ts

@@ -0,0 +1,2 @@
+export { Checkbox, default } from './Checkbox';
+export type { CheckboxProps } from './Checkbox';

src/components/pages/PaymentStep/PaymentStep.tsx

@@ -1,7 +1,7 @@
 import React from 'react';
 import Box from '@mui/material/Box';
 import Paper from '@mui/material/Paper';
-import Checkbox from '@mui/material/Checkbox';
+import { Checkbox } from '../../atoms/Checkbox';
 import FormControlLabel from '@mui/material/FormControlLabel';
 import type { SxProps, Theme } from '@mui/material/styles';
 import LockOutlinedIcon from '@mui/icons-material/LockOutlined';

src/theme/index.ts

@@ -783,6 +783,32 @@ export const theme = createTheme({
         },
       },
     },
+    MuiCheckbox: {
+      styleOverrides: {
+        root: {
+          color: t.ColorNeutral400,
+          transition: 'color 150ms ease-in-out',
+          '&:hover': {
+            color: t.ColorNeutral600,
+            backgroundColor: 'transparent',
+          },
+          '&.Mui-checked': {
+            color: t.ColorInteractiveDefault,
+            '&:hover': {
+              color: t.ColorInteractiveHover,
+            },
+          },
+          '&:focus-visible': {
+            outline: `2px solid ${t.ColorInteractiveFocus}`,
+            outlineOffset: '2px',
+            borderRadius: '4px',
+          },
+          '&.Mui-disabled': {
+            color: t.ColorNeutral300,
+          },
+        },
+      },
+    },
     MuiRadio: {
       styleOverrides: {
         root: {