🐛 fix(ci): 补全 prepare.yml 缺失的 GIT_CONFIG_VALUE_1

GIT_CONFIG_COUNT=3 但 env 段漏写 GIT_CONFIG_KEY_1/VALUE_1，
credential helper 函数串被错放到 KEY_1，导致 git 报
missing config value GIT_CONFIG_VALUE_1 而无法 fetch。

.gitea/workflows/prepare.yml

@@ -13,7 +13,8 @@ env:
   GIT_CONFIG_COUNT: "3"
   GIT_CONFIG_KEY_0: "credential.helper"
   GIT_CONFIG_VALUE_0: ""
-  GIT_CONFIG_KEY_1: '!f() { test "$1" = get || exit 0; printf "%s\n" username=oauth2; printf "%s\n" "password=${ACCESS_TOKEN}"; }; f'
+  GIT_CONFIG_KEY_1: "credential.helper"
+  GIT_CONFIG_VALUE_1: '!f() { test "$1" = get || exit 0; printf "%s\n" username=oauth2; printf "%s\n" "password=${ACCESS_TOKEN}"; }; f'
   GIT_CONFIG_KEY_2: "credential.interactive"
   GIT_CONFIG_VALUE_2: "never"
   WORKSPACE_ROOT: "/data/workspace"