SDK sandbox provisioning: built-in providers, docs restructure, and quickstart overhaul

- Add built-in sandbox providers (local, docker, e2b, daytona, vercel, cloudflare) to the TypeScript SDK so users import directly instead of passing client instances
- Restructure docs: rename architecture to orchestration-architecture, add new architecture page for server overview, improve getting started flow
- Rewrite quickstart to be TypeScript-first with provider CodeGroup and custom provider accordion
- Update all examples to use new provider APIs
- Update persist drivers and foundry for new SDK surface

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

examples/boxlite/src/index.ts

@@ -25,7 +25,7 @@ const baseUrl = "http://localhost:3000";
 
 console.log("Connecting to server...");
 const client = await SandboxAgent.connect({ baseUrl });
-const session = await client.createSession({ agent: detectAgent(), sessionInit: { cwd: "/root", mcpServers: [] } });
+const session = await client.createSession({ agent: detectAgent(), cwd: "/root" });
 const sessionId = session.id;
 
 console.log(`  UI: ${buildInspectorUrl({ baseUrl, sessionId })}`);