fix(jira_env): 为JIRA_BASE_URL添加默认值并优化错误提示

修改require_credentials函数，为JIRA_BASE_URL添加默认值"https://n2nafe.atlassian.net"
优化错误提示信息，明确指导用户如何配置和获取API token

skills/g3fo-commit-jira/scripts/jira_env.py

@@ -50,13 +50,14 @@ def load_config(config_path: Optional[str] = None, script_dir: Optional[Path] =
 
 
 def require_credentials(cfg: Dict[str, str]) -> tuple:
-    base_url = (cfg.get("JIRA_BASE_URL") or "").rstrip("/")
+    base_url = (cfg.get("JIRA_BASE_URL") or "https://n2nafe.atlassian.net").rstrip("/")
     email = cfg.get("JIRA_EMAIL")
     token = cfg.get("JIRA_API_TOKEN")
-    if not base_url or not email or not token:
+    if not email or not token:
         raise ValueError(
-            "Missing JIRA_BASE_URL, JIRA_EMAIL, or JIRA_API_TOKEN. "
-            f"Set in {CONFIG_FILENAME} or environment (see references/env_config.md)."
+            "Missing JIRA_EMAIL or JIRA_API_TOKEN. "
+            f"Please configure {CONFIG_FILENAME} file first. "
+            f"You can apply for API token at: https://id.atlassian.com/manage-profile/security/api-tokens"
         )
     return base_url, email, token