docs: Add TypeScript SDK reference documentation

## Summary
Complete reference documentation for the TypeScript MCP Server SDK (arcade-mcp),
providing feature parity with the Python SDK while using TypeScript-idiomatic patterns.

## New Files
- `typescript/overview/` - MCPApp API, tool registration, Zod 4 schemas
- `typescript/types/` - ToolContext, ContentItem, protocol types, schema utilities
- `typescript/errors/` - Complete error hierarchy with constructor signatures
- `typescript/middleware/` - MCP middleware and HTTP hooks via app.elysia
- `typescript/server/` - Low-level MCPServer class for custom transports
- `typescript/transports/` - stdio and HTTP transport modes
- `typescript/settings/` - MCPSettings, environment variables, configuration

## Design Decisions

### Options Object Pattern
TypeScript uses options objects for error constructors (vs Python positional args):
```typescript
throw new ContextRequiredToolError('Message', {
  additionalPromptContent: 'Please specify...',  // required
  developerMessage: 'debug info',                // optional
});
```

### HTTP Hooks via app.elysia
Clean separation - MCPApp handles MCP, app.elysia handles HTTP:
```typescript
app.elysia.onRequest(({ request }) => { ... });
```

### Runtime Tool Registration
materializeTool() creates tool objects for runtime addition:
```typescript
const tool = materializeTool({ name, input, handler });
await app.tools.add(tool);
```

## Stack
Bun 1.3.x + Elysia 1.3.x + Zod 4.x + TypeScript 5.9.x

## Related
- Python SDK docs: /references/mcp/python/
- Depends on: #XX (Python error hierarchy improvements) - for consistent error docs

Author: TheMostlyGreat

app/en/references/mcp/_meta.tsx

@@ -11,6 +11,9 @@ const meta: MetaRecord = {
   python: {
     title: "Python",
   },
+  typescript: {
+    title: "TypeScript",
+  },
   telemetry: {
     title: "Telemetry",
   },

app/en/references/mcp/typescript/_meta.tsx

@@ -0,0 +1,35 @@
+import type { MetaRecord } from "nextra";
+
+const meta: MetaRecord = {
+  "*": {
+    theme: {
+      breadcrumb: true,
+      layout: "full",
+      toc: true,
+      copyPage: true,
+    },
+  },
+  overview: {
+    title: "Overview",
+  },
+  transports: {
+    title: "Transports",
+  },
+  server: {
+    title: "Server",
+  },
+  middleware: {
+    title: "Middleware",
+  },
+  types: {
+    title: "Types",
+  },
+  errors: {
+    title: "Errors",
+  },
+  settings: {
+    title: "Settings",
+  },
+};
+
+export default meta;