feat(phase-4): WS2 + WS3 — Developer Portal (Next.js 14) and CLI tool (sentryagent)

WS2: Developer Portal (portal/)
- Standalone Next.js 14 + Tailwind CSS app — independent deployment
- Home page: hero, feature grid, CTA to /get-started
- /pricing: free tier limits table (10 agents, 1k calls/day) + paid tier CTA
- /sdks: all 4 SDKs (Node.js, Python, Go, Java) with install + code examples
- /api-explorer: Swagger UI from NEXT_PUBLIC_API_URL/openapi.json, persistAuthorization
- /get-started: 4-step wizard (setup → register agent → credentials → SDK snippet)
- Shared Nav component with active-link highlighting
- Build: 8/8 static pages, zero TypeScript errors

WS3: CLI Tool (cli/ — npm package: sentryagent)
- configure, register-agent, list-agents, issue-token, rotate-credentials, tail-audit-log
- Auto OAuth2 token fetch + 30s-buffer cache via client_credentials flow
- chalk-formatted table output, confirmation prompts, bounded audit log dedup
- bash + zsh shell completion scripts
- README with installation, all commands, and completion setup
- Build: tsc clean, node dist/index.js --help verified

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

portal/app/api-explorer/page.tsx

@@ -0,0 +1,38 @@
+import type React from 'react';
+import { SwaggerExplorer } from '@/components/SwaggerExplorer';
+
+export const metadata = {
+  title: 'API Explorer — SentryAgent AgentIdP',
+  description:
+    'Interactively explore and test the SentryAgent AgentIdP REST API.',
+};
+
+export default function ApiExplorerPage(): React.ReactElement {
+  const apiUrl =
+    process.env.NEXT_PUBLIC_API_URL ?? 'http://localhost:3000';
+
+  return (
+    <div className="px-4 py-8">
+      <div className="mx-auto max-w-7xl">
+        <div className="mb-8">
+          <h1 className="text-3xl font-extrabold text-slate-900">
+            API Explorer
+          </h1>
+          <p className="mt-2 text-slate-600">
+            Explore, authenticate, and test every AgentIdP endpoint directly
+            from your browser. Use the Authorize button to set your Bearer
+            token.
+          </p>
+          <p className="mt-1 text-sm text-slate-400">
+            Spec loaded from:{' '}
+            <code className="rounded bg-slate-100 px-1.5 py-0.5 text-xs">
+              {apiUrl}/openapi.json
+            </code>
+          </p>
+        </div>
+
+        <SwaggerExplorer apiUrl={apiUrl} />
+      </div>
+    </div>
+  );
+}