chore(xaf_agent_hub): 统一实例模型链为 opencode free/axonhub/agnes，prod-etotem 第二档 etotem/deepseek 且口令 OpenCode@123

- 全部实例 model_chain 统一为 opencode/deepseek-v4.1-flash-free -> axonhub/deepseek -> agnes/agnes-3.0-flash
- prod-etotem 例外：第二档换为 etotem/deepseek（用户 2026-11-06 裁定）
- prod-etotem password 直接写入 OpenCode@123（保留 password_env 备选）
- 移除 nvidia/nemotron 与 axon 候选列表槽位

tools/xaf_agent_hub/config.json

@@ -52,6 +52,11 @@
       ],
       "default_directory": "E:\\cfc",
       "fallback_model": "axonhub/deepseek",
+      "model_chain": [
+        "opencode/deepseek-v4.1-flash-free",
+        "axonhub/deepseek",
+        "agnes/agnes-3.0-flash"
+      ],
       "concurrency_limit": 6,
       "branch_policy": "mainline"
     },
@@ -69,7 +74,6 @@
       "model_chain": [
         "opencode/deepseek-v4.1-flash-free",
         "axonhub/deepseek",
-        "nvidia/nvidia/nemotron-3-ultra-550b-a55b",
         "agnes/agnes-3.0-flash"
       ]
     },
@@ -83,6 +87,11 @@
       ],
       "default_directory": "D:\\cfc",
       "fallback_model": "axonhub/deepseek",
+      "model_chain": [
+        "opencode/deepseek-v4.1-flash-free",
+        "axonhub/deepseek",
+        "agnes/agnes-3.0-flash"
+      ],
       "concurrency_limit": 4,
       "branch_policy": "mainline",
       "dir_aliases": {
@@ -102,11 +111,8 @@
       "concurrency_limit": 4,
       "model_chain": [
         "opencode/deepseek-v4.1-flash-free",
-        [
-          "axonhub/deepseek",
-          "axon/deepseek"
-        ],
-        "nvidia/nvidia/nemotron-3-ultra-550b-a55b"
+        "axonhub/deepseek",
+        "agnes/agnes-3.0-flash"
       ],
       "dir_aliases": {
         "/sc-data/cfc": "C:/code/cfc"
@@ -115,7 +121,7 @@
     {
       "name": "prod-etotem",
       "base_url": "https://opencode.etotem.com.cn",
-      "password": null,
+      "password": "OpenCode@123",
       "password_env": "XAF_HUB_PW_PROD_ETOTEM",
       "cfc_roots": [
         "/root/cfc",
@@ -125,6 +131,11 @@
       "danger": true,
       "readonly_default": true,
       "fallback_model": "axonhub/deepseek",
+      "model_chain": [
+        "opencode/deepseek-v4.1-flash-free",
+        "etotem/deepseek",
+        "agnes/agnes-3.0-flash"
+      ],
       "concurrency_limit": 4,
       "auto_prod": true
     },
@@ -139,6 +150,11 @@
       ],
       "default_directory": "/sc-data/cfc",
       "fallback_model": "etotem/deepseek",
+      "model_chain": [
+        "opencode/deepseek-v4.1-flash-free",
+        "axonhub/deepseek",
+        "agnes/agnes-3.0-flash"
+      ],
       "concurrency_limit": 6
     }
   ],