V48 Gate 3 (implementation-only): staging-testnet bring-up targets the shared staginglocal-testnet Vercel environment

One Vercel custom environment serves both staging-testnet and
local-testnet (custom-env limit of 1); the bring-up script's default
VERCEL_TARGET follows.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: geraldarthurdavis

scripts/bringup-staging-testnet.sh

@@ -21,7 +21,7 @@ PROJECT_REF="mwugicjpxmrtctvjghjg"
 SUPABASE_URL="https://${PROJECT_REF}.supabase.co"
 SECRETS_FILE="$(dirname "$0")/.env.staging-testnet"
 # Vercel custom environment the testnet.bitcode.exchange domain is attached to.
-VERCEL_TARGET="${VERCEL_TARGET:-staging-testnet}"
+VERCEL_TARGET="${VERCEL_TARGET:-staginglocal-testnet}"
 
 require_secrets() {
   if [[ ! -f "$SECRETS_FILE" ]]; then