feat: implement CAIP25 MultiChain API and NextJS playground integration

[abretonc7s]

Description

This PR implements a new MultiChain API package that follows the CAIP25 specification to provide chain-agnostic wallet interactions. It also includes a Next.js playground for testing and demonstrating the API capabilities.

Key Features

• New @metamask/multichainapi package implementing CAIP25 spec
• Interactive Next.js playground for testing multichain functionality
• Integration with MetaMask extension for cross-chain operations
• Support for session management and chain-specific method invocation
• Rich validation and testing environment

MultiChain API Implementation

• Implements CAIP25 session management (create/get/revoke)
• Supports method invocation across different chains
• Handles wallet discovery and connection
• Event system for session changes and notifications
• Built-in TypeScript support and full type safety

Next.js Playground Features

• Interactive UI for testing CAIP25 functionality
• Session lifecycle management
• Chain selection and method invocation
• Real-time response visualization
• Comprehensive error handling

Implementation Details

• Uses Turborepo for improved monorepo development
• Implements proper validation for message sizes and payloads
• Handles extension and deep-link communication
• Supports different environments (extension, mobile web, desktop)
• Includes thorough unit tests
• Configurable logging and debugging support

Testing Instructions

1. Build and run the playground:

yarn install
yarn dev:core
cd packages/playground-next
yarn dev

2. Test core functionality:

• Connect to MetaMask extension
• Create sessions with different chain selections
• Invoke methods across chains
• Monitor session changes and notifications
• Test error handling and validation

Documentation

The playground serves as living documentation for the MultiChain API. Additional package documentation will be added in follow-up PRs.

Review Checklist

• Review CAIP25 compliance
• Test session management across different chains
• Verify error handling and validation
• Check playground functionality
• Review TypeScript types and API surface
• Test extension integration
• Verify build process and dependencies

[socket-security]

New dependencies detected. Learn more about Socket for GitHub ↗︎

Package	New capabilities	Transitives	Size	Publisher
npm/@babel/[email protected]	network	0	34.3 kB	nicolo-ribaudo
npm/@babel/[email protected]	network	0	15.7 kB	nicolo-ribaudo
npm/@metamask/[email protected]	None	0	275 kB	metamaskbot
npm/@open-rpc/[email protected]	None	0	38.4 kB	belfordz
npm/@types/[email protected]	None	+2	843 kB	types
npm/[email protected]	None	0	155 kB	kilianvalkhof

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[socket-security]

🚨 Potential security issues detected. Learn more about Socket for GitHub ↗︎

To accept the risk, merge this PR and you will not be notified again.

Alert	Package	Note	Source	CI
New author	npm/@lavamoat/[email protected]	New Author: lmbot Previous Author: naugtur	Source	🚫
Install scripts	npm/@lavamoat/[email protected]	Install script: preinstall Source: echo "Don't run npm lifecycle scripts by default! Create a .yarnrc or .npmrc and set enableScripts: false. Then, whitelist them with @lavamoat/allow-scripts" && exit 1	Source	⚠︎
Network access	npm/@babel/[email protected]	Module: globalThis["fetch"] Location: Package overview	packages/examples/nextjs-demo/yarn.lock	🚫
Network access	npm/@babel/[email protected]	Module: globalThis["fetch"] Location: Package overview	packages/examples/nextjs-demo/package.json packages/examples/nextjs-demo/yarn.lock	🚫

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