feat: add server helpers, make connect() to default to parent post transport (#165)

* feat: add server helpers and optional connect() transport

Add `src/server/` with convenience functions for registering MCP App tools
and resources:

- `registerAppTool(server, name, config, handler)`
- `registerAppResource(server, name, uri, config, callback)`

The `transport` parameter in `App.connect()` is now optional, defaulting to
`PostMessageTransport(window.parent)`.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

* Update src/server/index.ts

Co-authored-by: Jonathan Hefner <jonathan@hefner.pro>

* fix: refine server helper types

- Make RESOURCE_URI_META_KEY required in McpUiAppToolConfig (tools need a UI resource)
- Make _meta optional in McpUiAppResourceConfig (not all resources need custom metadata)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

* refactor: simplify RESOURCE_URI_META_KEY re-export

* refactor: consolidate export statements

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Jonathan Hefner <jonathan@hefner.pro>

examples/wiki-explorer-server/src/mcp-app.ts

@@ -1,7 +1,7 @@
 /**
  * Wiki Explorer - Force-directed graph visualization of Wikipedia link networks
  */
-import { App, PostMessageTransport } from "@modelcontextprotocol/ext-apps";
+import { App } from "@modelcontextprotocol/ext-apps";
 import type { CallToolResult } from "@modelcontextprotocol/sdk/types.js";
 import {
   forceCenter,
@@ -367,4 +367,4 @@ app.onerror = (err) => {
 };
 
 // Connect to host
-app.connect(new PostMessageTransport(window.parent));
+app.connect();