feat: improve empty state guidance for first-run experience

Show detailed import instructions and conditionally display common
config snippet hint for Claude/Codex/Gemini (not OpenCode/OpenClaw).

src/components/providers/ProviderEmptyState.tsx

@@ -1,17 +1,22 @@
 import { Download, Users } from "lucide-react";
 import { useTranslation } from "react-i18next";
 import { Button } from "@/components/ui/button";
+import type { AppId } from "@/lib/api/types";
 
 interface ProviderEmptyStateProps {
+  appId: AppId;
   onCreate?: () => void;
   onImport?: () => void;
 }
 
 export function ProviderEmptyState({
+  appId,
   onCreate,
   onImport,
 }: ProviderEmptyStateProps) {
   const { t } = useTranslation();
+  const showSnippetHint =
+    appId === "claude" || appId === "codex" || appId === "gemini";
 
   return (
     <div className="flex flex-col items-center justify-center rounded-lg border border-dashed border-border p-10 text-center">
@@ -19,9 +24,14 @@ export function ProviderEmptyState({
         <Users className="h-7 w-7 text-muted-foreground" />
       </div>
       <h3 className="text-lg font-semibold">{t("provider.noProviders")}</h3>
-      <p className="mt-2 max-w-sm text-sm text-muted-foreground">
+      <p className="mt-2 max-w-lg text-sm text-muted-foreground">
         {t("provider.noProvidersDescription")}
       </p>
+      {showSnippetHint && (
+        <p className="mt-1 max-w-lg text-sm text-muted-foreground">
+          {t("provider.noProvidersDescriptionSnippet")}
+        </p>
+      )}
       <div className="mt-6 flex flex-col gap-2">
         {onImport && (
           <Button onClick={onImport}>

src/components/providers/ProviderList.tsx

@@ -298,6 +298,7 @@ export function ProviderList({
   if (sortedProviders.length === 0) {
     return (
       <ProviderEmptyState
+        appId={appId}
         onCreate={onCreate}
         onImport={() => importMutation.mutate()}
       />