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/ar.json

@@ -626,7 +626,13 @@
       "reasoningModel": "نموذج الاستدلال (thinking)",
       "haikuDefaultModel": "نموذج Haiku الافتراضي",
       "sonnetDefaultModel": "نموذج Sonnet الافتراضي",
-      "opusDefaultModel": "نموذج Opus الافتراضي"
+      "opusDefaultModel": "نموذج Opus الافتراضي",
+      "effortLevel": "مستوى الاستدلال",
+      "effortLevelDefault": "المستوى الافتراضي",
+      "effortLevel_low": "منخفض",
+      "effortLevel_medium": "متوسط",
+      "effortLevel_high": "مرتفع",
+      "effortLevelMax": "الأقصى (Opus فقط)"
     },
     "dialogs": {
       "confirmDeleteProvider": "حذف المزود {providerId}؟",