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>

docs/sdk-overview.mdx

@@ -84,25 +84,40 @@ const sdk = await SandboxAgent.connect({
 });
 ```
 
-Local autospawn (Node.js only):
+Local spawn with a sandbox provider:
 
 ```ts
 import { SandboxAgent } from "sandbox-agent";
+import { local } from "sandbox-agent/local";
 
-const localSdk = await SandboxAgent.start();
+const sdk = await SandboxAgent.start({
+  sandbox: local(),
+});
 
-await localSdk.dispose();
+// sdk.sandboxId — prefixed provider ID (e.g. "local/127.0.0.1:2468")
+
+await sdk.destroySandbox(); // tears down sandbox + disposes client
 ```
 
+`SandboxAgent.start(...)` requires a `sandbox` provider. Built-in providers:
+
+| Import | Provider |
+|--------|----------|
+| `sandbox-agent/local` | Local subprocess |
+| `sandbox-agent/docker` | Docker container |
+| `sandbox-agent/e2b` | E2B sandbox |
+| `sandbox-agent/daytona` | Daytona workspace |
+| `sandbox-agent/vercel` | Vercel Sandbox |
+| `sandbox-agent/cloudflare` | Cloudflare Sandbox |
+
+Use `sdk.dispose()` to disconnect without destroying the sandbox, or `sdk.destroySandbox()` to tear down both.
+
 ## Session flow
 
 ```ts
 const session = await sdk.createSession({
   agent: "mock",
-  sessionInit: {
-    cwd: "/",
-    mcpServers: [],
-  },
+  cwd: "/",
 });
 
 const prompt = await session.prompt([
@@ -223,6 +238,7 @@ Parameters:
 - `token` (optional): Bearer token for authenticated servers
 - `headers` (optional): Additional request headers
 - `fetch` (optional): Custom fetch implementation used by SDK HTTP and session calls
+- `skipHealthCheck` (optional): set `true` to skip the startup `/v1/health` wait
 - `waitForHealth` (optional, defaults to enabled): waits for `/v1/health` before HTTP helpers and session setup proceed; pass `false` to disable or `{ timeoutMs }` to bound the wait
 - `signal` (optional): aborts the startup `/v1/health` wait used by `connect()`