docs(sca): add quote-scoped resend + note withheld paymentInstructions

Address Greptile review on #683:
- Document the quote resend endpoint (POST /quotes/{quoteId}/authorize/resend)
  alongside the transaction one, since a realtime-funding quote's SMS challenge
  exists before any transaction.
- Note that a realtime-funding 202 withholds paymentInstructions until the
  challenge is authorized, so integrators authorize first, then read them.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: jklein24

mintlify/snippets/sca/strong-customer-authentication.mdx

@@ -82,8 +82,20 @@ authorize endpoint for the resource:
 </Step>
 </Steps>
 
+<Note>
+For a **realtime-funding quote**, the `202` / `PENDING_AUTHORIZATION` response
+**withholds `paymentInstructions`** until the challenge is authorized. Authorize
+first, then read `paymentInstructions` from the returned (advanced) quote — don't
+read them off the initial pending response, or you'll show the customer nothing
+to fund.
+</Note>
+
 If an SMS code lapses before it's used, re-send it (the existing challenge is
-reused, and its `expiresAt` is not extended):
+reused, and its `expiresAt` is not extended). Use the resend endpoint for the
+resource that carries the challenge:
+
+- Transaction (after `execute` / `transfer-out`): `POST /transactions/{transactionId}/authorize/resend`
+- Realtime-funding quote (from `POST /quotes`): `POST /quotes/{quoteId}/authorize/resend`
 
 ```bash
 curl -X POST https://api.lightspark.com/grid/2025-10-13/transactions/{transactionId}/authorize/resend \