refactor: 优化模型配置与统一命名格式

- 将多个模型的配置项 variant 从 xhigh 调整为 medium 或 high，以优化性能与资源使用平衡。
- 将模型名称格式统一为连字符命名，提升命名一致性。

oh-my-opencode.jsonc

@@ -9,14 +9,14 @@
     },
     "hephaestus": {
       "model": "cpa-openai/gpt-5.3-codex",
-      "variant": "xhigh"
+      "variant": "medium"
     },
     "atlas": {
       "model": "cpa-anthropic/claude-sonnet-4-5"
     },
     "oracle": {
       "model": "cpa-openai/gpt-5.2",
-      "variant": "xhigh"
+      "variant": "high"
     },
     "librarian": {
       "model": "cpa-google/gemini-3-flash"
@@ -37,7 +37,7 @@
     },
     "momus": {
       "model": "cpa-openai/gpt-5.2",
-      "variant": "xhigh"
+      "variant": "medium"
     },
     "sisyphus-junior": {
       "model": "cpa-anthropic/claude-sonnet-4-5"
@@ -55,11 +55,11 @@
     },
     "deep": {
       "model": "cpa-openai/gpt-5.3-codex",
-      "variant": "xhigh"
+      "variant": "medium"
     },
     "artistry": {
       "model": "cpa-google/gemini-3-pro",
-      "variant": "max"
+      "variant": "high"
     },
     "quick": {
       "model": "cpa-google/gemini-3-flash"