feat(ui): dynamic endpoint hint based on API format selection (#860)

- Add apiHintOAI i18n key for OpenAI Chat Completions format hint
- Update ClaudeFormFields to show format-specific endpoint hints
- When API format is "openai_chat", show OAI-specific hint
- Maintains consistency between hint and selected API format

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

src/components/providers/forms/ClaudeFormFields.tsx

@@ -163,7 +163,11 @@ export function ClaudeFormFields({
           value={baseUrl}
           onChange={onBaseUrlChange}
           placeholder={t("providerForm.apiEndpointPlaceholder")}
-          hint={t("providerForm.apiHint")}
+          hint={
+            apiFormat === "openai_chat"
+              ? t("providerForm.apiHintOAI")
+              : t("providerForm.apiHint")
+          }
           onManageClick={() => onEndpointModalToggle(true)}
         />
       )}