[macos-runner] Guard checkout against hanging on prompts or a stalled clone

git clone froze for 9+ minutes on one run with no clear cause. Set
GIT_TERMINAL_PROMPT=0 so it fails fast instead of hanging if credential
auth ever goes wrong, and abort via http.lowSpeedLimit/lowSpeedTime if
the transfer genuinely stalls instead of just being slow.

.gitea/workflows/beta.yml

@@ -24,9 +24,10 @@ jobs:
     steps:
       - name: Checkout
         run: |
+          export GIT_TERMINAL_PROMPT=0
           REPO_URL="${{ gitea.server_url }}/${{ gitea.repository }}.git"
           AUTH_URL="$(echo "$REPO_URL" | sed "s#https://#https://x-access-token:${{ gitea.token }}@#")"
-          git clone "$AUTH_URL" .
+          git -c http.lowSpeedLimit=1000 -c http.lowSpeedTime=30 clone "$AUTH_URL" .
           git checkout "${{ gitea.sha }}"
 
       - name: Set build number