feat(settings): add reasoning effort level for Claude Code

Add an Effort Level dropdown under the Claude Code model inputs with
options Low / Medium / High / Max (Opus only). The selection writes an
"effortLevel" key at the root of the Claude Code config JSON, and is
removed when the default is chosen. Manual edits to the native JSON
textarea stay in sync with the dropdown.

src/i18n/messages/zh-TW.json

@@ -626,7 +626,13 @@
       "reasoningModel": "推理模型（thinking）",
       "haikuDefaultModel": "Haiku 預設模型",
       "sonnetDefaultModel": "Sonnet 預設模型",
-      "opusDefaultModel": "Opus 預設模型"
+      "opusDefaultModel": "Opus 預設模型",
+      "effortLevel": "推理等級",
+      "effortLevelDefault": "預設等級",
+      "effortLevel_low": "低",
+      "effortLevel_medium": "中",
+      "effortLevel_high": "高",
+      "effortLevelMax": "最高（僅 Opus 支援）"
     },
     "dialogs": {
       "confirmDeleteProvider": "確認刪除 Provider {providerId}？",