feat(phase-5): WS5 — Developer Experience

Implements scaffold ZIP generator, Stoplight Elements API explorer, and CLI scaffold command:

Scaffold API:
- 25 template files for TypeScript/Python/Go/Java/Rust in src/templates/scaffold/
- ScaffoldService: in-memory ZIP via archiver, variable injection (AGENT_ID/NAME/CLIENT_ID/API_URL)
- ScaffoldController: tenant ownership check (403), language validation (400), ZIP stream response
- Route GET /sdk/scaffold/:agentId with rate limiter (10 req/min per tenant)
- Prometheus: scaffold_generated_total + scaffold_generation_duration_ms histogram

Portal:
- Replaced swagger-ui-react with @stoplight/elements API component
- Dynamic import (ssr: false) for browser-only DOM dependency
- Type declarations for @stoplight/elements and CSS module

CLI:
- sentryagent scaffold --agent-id <id> [--language typescript] [--out .]
- Raw fetch for binary ZIP stream → unzipper.Extract() → prints next steps
- Human-readable 400/403/404 error messages

Tests: 19 tests (unit + integration), ScaffoldService 80%+ branch coverage

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

portal/app/api-explorer/page.tsx

@@ -1,38 +1,28 @@
-import type React from 'react';
-import { SwaggerExplorer } from '@/components/SwaggerExplorer';
+'use client';
 
-export const metadata = {
-  title: 'API Explorer — SentryAgent AgentIdP',
-  description:
-    'Interactively explore and test the SentryAgent AgentIdP REST API.',
-};
+import dynamic from 'next/dynamic';
 
-export default function ApiExplorerPage(): React.ReactElement {
-  const apiUrl =
-    process.env.NEXT_PUBLIC_API_URL ?? 'http://localhost:3000';
+// @stoplight/elements accesses `document` at module load time,
+// so it must be imported client-side only (ssr: false).
+const ElementsAPI = dynamic(
+  async () => {
+    await import('@stoplight/elements/styles.min.css');
+    const mod = await import('@stoplight/elements');
+    return mod.API;
+  },
+  { ssr: false },
+);
 
+export default function ApiExplorerPage() {
   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>
+    <main className="h-screen w-full">
+      <ElementsAPI
+        apiDescriptionUrl={`${process.env.NEXT_PUBLIC_API_URL}/openapi.json`}
+        router="hash"
+        layout="sidebar"
+        hideSchemas={false}
+        tryItCredentialsPolicy="same-origin"
+      />
+    </main>
   );
 }