fix(api): support absolute paths in BaseApiClient.request()

When path starts with /api/, treat it as an absolute URL instead of
prepending baseUrl. This fixes installSkill/uninstallSkill URL
concatenation that produced /api/v1/skill-management/api/v1/skills/...

src/agentkit/server/frontend/src/api/base.ts

@@ -14,7 +14,8 @@ export class BaseApiClient {
   }
 
   protected async request<T>(path: string, options: RequestInit = {}): Promise<T> {
-    const url = `${this.baseUrl}${path}`
+    // If path starts with /api/, it's an absolute path — don't prepend baseUrl
+    const url = path.startsWith('/api/') ? path : `${this.baseUrl}${path}`
     const headers: Record<string, string> = {
       ...options.headers as Record<string, string>,
     }