feat: 更新ultrabrain模型配置并调整推理强度

- 更新ultrabrain模型配置为gpt-5.2-codex版本
- 将 GPT-5.2 和 GPT-5.2-Codex 模型的推理强度配置为 xhigh，并移除冗余的模型条目。

oh-my-opencode.jsonc

@@ -35,7 +35,7 @@
       "model": "cpa-google/gemini-3-pro-high"
     },
     "ultrabrain": {
-      "model": "packy-openai/gpt-5.2-codex-xhigh"
+      "model": "packy-openai/gpt-5.2-codex"
     },
     "artistry": {
       "model": "cpa-google/gemini-3-pro-high"

opencode.jsonc

@@ -53,17 +53,17 @@
         "setCacheKey": true
       },
       "models": {
-        "gpt-5.2-xhigh": {
-          "name": "GPT-5.2 (xhigh)"
-        },
         "gpt-5.2": {
-          "name": "GPT-5.2"
-        },
-        "gpt-5.2-codex-xhigh": {
-          "name": "GPT-5.2-Codex (xhigh)"
+          "name": "GPT-5.2",
+          "options": {
+            "reasoningEffort": "xhigh"
+          }
         },
         "gpt-5.2-codex": {
-          "name": "GPT-5.2-Codex"
+          "name": "GPT-5.2-Codex",
+          "options": {
+            "reasoningEffort": "xhigh"
+          }
         }
       }
     }