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

[ochafik]

Summary

Server Helpers (src/server/)

Add convenience functions for registering MCP App tools and resources:

• registerAppTool(server, name, config, handler) - registers a tool with _meta[RESOURCE_URI_META_KEY] for the UI resource URI
• registerAppResource(server, name, uri, config, callback) - registers a resource with default MIME type text/html;profile=mcp-app

The helpers will allow transparent migrations, e.g. making #131 backwards-compatible + more type-safe (ui can be defined as a key on McpUiAppToolConfig._meta, which otherwise only accepts indexed keys)

Optional Transport in App.connect()

The transport parameter in App.connect() is now optional:

• Defaults to PostMessageTransport(window.parent) when not provided
• Simplifies app initialization: await app.connect() just works

Example Updates

Updated all examples to use the new helpers and package imports (@modelcontextprotocol/ext-apps/server).

Test plan

• Unit tests for registerAppTool and registerAppResource
• Build passes (npm run build:all)
• All existing tests pass

🤖 Generated with Claude Code

[pkg-pr-new]

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npm i https://pkg.pr.new/modelcontextprotocol/ext-apps/@modelcontextprotocol/ext-apps@165

commit: 82322a7

[jonathanhefner]

Food for thought: if there are other MCP extensions that similarly rely on _meta properties (on tools or resources), and they also want to define their own register*Tool() or register*Resource() helpers, those would clash ours.

A lighter-touch approach might be helper functions that accept and return preconfigured ToolConfig and ResourceMetadata objects. (Then you could write appToolConfig(fooToolConfig(barToolConfig({ ... }))).)

Anyway, not a blocker.