feat(uat-batch-23): supplemental-info — separate Generate link + Send by email

The single-button "Request more info" conflated link generation with
email send. Once tokens became reusable until expiry (PR15), the
two-step UX makes more sense — reps often need to copy the link and
share it via WhatsApp / iMessage instead of letting SMTP route it.

- API: POST /supplemental-info-request now accepts an optional
  `{ sendEmail?: boolean }` body (defaults true for back-compat).
  Generate-only callers pass `{ sendEmail: false }`.
- UI: two buttons replace the single CTA — "Generate link" (always
  generates, never emails) + "Send by email" (the original
  full-blow behaviour). Re-clicking "Generate link" with a token
  already issued mints a fresh one (labeled "Regenerate link").
- Email body copy: drop "can only be used once" since PR15 made the
  link reusable until expiry.

tsc clean. 1419/1419 vitest pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/interests/supplemental-info-request-button.tsx

@@ -40,16 +40,19 @@ export function SupplementalInfoRequestButton({ interestId, eoiStatus }: Props)
   const [link, setLink] = useState<string | null>(null);
 
   const mutation = useMutation({
-    mutationFn: () =>
+    mutationFn: (vars: { sendEmail: boolean }) =>
       apiFetch<IssueResponse>(`/api/v1/interests/${interestId}/supplemental-info-request`, {
         method: 'POST',
+        body: vars,
       }),
     onSuccess: (res) => {
       setLink(res.data.link);
       if (res.data.emailSent) {
-        toast.success('Email sent — link also shown below for sharing manually.');
+        toast.success('Email sent. Link also shown below for sharing manually.');
       } else {
-        toast.message('Link generated — no client email on file, share manually.');
+        toast.message(
+          'Link generated. Click "Send by email" to mail it, or copy it to share manually.',
+        );
       }
     },
     onError: (err) =>
@@ -76,11 +79,20 @@ export function SupplementalInfoRequestButton({ interestId, eoiStatus }: Props)
           <Button
             type="button"
             size="sm"
-            onClick={() => mutation.mutate()}
+            variant={link ? 'outline' : 'default'}
+            onClick={() => mutation.mutate({ sendEmail: false })}
+            disabled={mutation.isPending}
+          >
+            {mutation.isPending ? 'Generating…' : link ? 'Regenerate link' : 'Generate link'}
+          </Button>
+          <Button
+            type="button"
+            size="sm"
+            onClick={() => mutation.mutate({ sendEmail: true })}
             disabled={mutation.isPending}
           >
             <Mail className="mr-1.5 size-3.5" aria-hidden />
-            {mutation.isPending ? 'Generating…' : link ? 'Resend' : 'Request more info'}
+            {link ? 'Send by email' : 'Generate + email'}
           </Button>
           {link ? (
             <>