Groom wizard steps 1-15: critique/harden/polish pass

- [P0] CrematoriumStep: Fix <option> → <MenuItem> in priority select
- [P1] All form steps: Add aria-busy={loading} + loading guard on submit
- [P1] Error messages: Replace color="error" (red) with copper
  (var(--fa-color-text-brand)) across ProvidersStep, PackagesStep,
  VenueStep, CrematoriumStep, CemeteryStep, CoffinsStep, PaymentStep
- [P2] IntroStep: "Has the person died?" → "Has this person passed away?"
- [P2] DateTimeStep: "About the person who died" → "who has passed"
- [P2] ProvidersStep: "Showing results from X" → "X providers found"
- [P2] Empty states: Add guidance text for ProvidersStep, PackagesStep,
  VenueStep, CoffinsStep empty results

Steps 4, 13, 15 passed with no issues.

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

src/components/pages/CrematoriumStep/CrematoriumStep.tsx

@@ -1,6 +1,7 @@
 import React from 'react';
 import Box from '@mui/material/Box';
 import TextField from '@mui/material/TextField';
+import MenuItem from '@mui/material/MenuItem';
 import FormControl from '@mui/material/FormControl';
 import FormLabel from '@mui/material/FormLabel';
 import FormControlLabel from '@mui/material/FormControlLabel';
@@ -151,9 +152,10 @@ export const CrematoriumStep: React.FC<CrematoriumStepProps> = ({
       <Box
         component="form"
         noValidate
+        aria-busy={loading}
         onSubmit={(e: React.FormEvent) => {
           e.preventDefault();
-          onContinue();
+          if (!loading) onContinue();
         }}
       >
         {/* ─── Crematorium selection ─── */}
@@ -226,7 +228,11 @@ export const CrematoriumStep: React.FC<CrematoriumStepProps> = ({
           )}
 
           {errors?.selectedCrematoriumId && (
-            <Typography variant="body2" color="error" sx={{ mt: 1 }} role="alert">
+            <Typography
+              variant="body2"
+              sx={{ mt: 1, color: 'var(--fa-color-text-brand)' }}
+              role="alert"
+            >
               {errors.selectedCrematoriumId}
             </Typography>
           )}
@@ -250,7 +256,11 @@ export const CrematoriumStep: React.FC<CrematoriumStepProps> = ({
             <FormControlLabel value="no" control={<Radio />} label="No" />
           </RadioGroup>
           {errors?.attend && (
-            <Typography variant="body2" color="error" sx={{ mt: 0.5 }} role="alert">
+            <Typography
+              variant="body2"
+              sx={{ mt: 0.5, color: 'var(--fa-color-text-brand)' }}
+              role="alert"
+            >
               {errors.attend}
             </Typography>
           )}
@@ -268,9 +278,9 @@ export const CrematoriumStep: React.FC<CrematoriumStepProps> = ({
             sx={{ mb: 3 }}
           >
             {priorityOptions.map((opt) => (
-              <option key={opt.value} value={opt.value}>
+              <MenuItem key={opt.value} value={opt.value}>
                 {opt.label}
-              </option>
+              </MenuItem>
             ))}
           </TextField>
         )}