Feat/metamask multichain

[GiMa-SwapKit]

feat(wallets): connect MetaMask via @metamask/connect-multichain (EVM + Solana)

Summary

Routes WalletOption.METAMASK through MetaMask's official multichain SDK
([@metamask/connect-multichain](https://docs.metamask.io/metamask-connect/multichain/))
instead of the legacy injected window.ethereum path. A single
[CAIP-25](https://github.com/ChainAgnostic/CAIPs/blob/main/CAIPs/caip-25.md)
session — and a single approval prompt — now covers EVM and Solana (and any
future ecosystem MetaMask adds), rather than a per-chain injected provider.

A new metamaskWallet connector exposes skClient.connectMetamask(chains, options?).
It lazily imports the SDK, derives supportedNetworks from each requested chain's
RPC URL, opens one session over all the requested CAIP-2 scopes, then adapts the
session into each toolbox SwapKit already has.

This is the multichain counterpart to the upstream @metamask/connect-evm work in
[swapkit/SwapKit#1632](swapkit/SwapKit#1632), chosen here
because the goal is EVM and Solana from one connection. connect-evm cannot do
Solana; the multichain client can, and per MetaMask's own guidance the two share
session infrastructure so this is the right long-term target.

Behavior change

• WalletOption.METAMASK no longer uses the injected window.ethereum provider.
  It is split out of the injected evmWallet group and routed to the new connector.
  The generic WalletOption.EIP6963 option still serves every other injected wallet.
• Selecting MetaMask can now authorize Solana in the same prompt as the EVM chains.

How it works

The multichain client has no per-chain EIP-1193 provider — all interaction goes
through invokeMethod({ scope, request }). The connector reshapes that into what
each existing SwapKit toolbox already consumes:

• EVM → a thin EIP-1193 shim over invokeMethod (it answers eth_accounts /
  eth_chainId from the session and forwards everything else to the wallet/RPC) →
  wrapped in an ethers BrowserProvider → fed to the existing getWeb3WalletMethods,
  unchanged.
• Solana → a SolanaProvider-style signer whose signTransaction calls
  solana_signTransaction (serialize → base64 → invoke → deserialize). It signs and
  returns; SwapKit broadcasts via its own sendRawTransaction, matching
  getSolanaToolbox({ signer }).
• Future ecosystems → add one adapter per ecosystem as SwapKit gains a toolbox.

Account resolution scans every sessionScopes bucket and matches accounts by their
CAIP-10 namespace:reference, so it is robust whether getSession returns full
CAIP-2 keys (eip155:1) or the namespace-collapsed form (eip155 + references).

Changes

Library

• packages/wallets/src/metamask/index.ts — new metamaskWallet connector (connectMetamask).
• packages/wallets/package.json — add @metamask/connect-multichain and @solana/web3.js; add ./metamask subpath export.
• packages/wallets/src/utils.ts — route METAMASK to the new connector (removed from the injected evmWallet group).
• packages/wallets/src/types.ts — repoint METAMASK types to metamaskWallet.
• packages/sdk/src/index.ts — register metamaskWallet in defaultWallets and re-export it.

Playground

• playgrounds/vite-lite/vite.config.ts — optimizeDeps config required to run the connect SDK (exclude @metamask/multichain-ui; include the dynamically-imported CJS deps).

Note: unlike upstream #1632, there is no libsodium-wrappers-sumo override here —
that dependency is not present in this repo's lockfile, so the fix doesn't apply.

Test plan

• bun run build:ci builds all packages and generates d.ts files cleanly.
• bun run type-check passes for every package, @swapkit/wallets and @swapkit/sdk included.
• Runtime, not yet verified — extension present: selecting MetaMask connects
  directly and resolves both an EVM and a Solana address from one prompt.
• Runtime, not yet verified — Solana solana_signTransaction round-trip
  (serialize → invoke → deserialize → SwapKit broadcast) and the EIP-1193 shim
  under a real BrowserProvider.

The runtime items need a UI to exercise them; vite-lite has no MetaMask button yet.
Happy to add one in a follow-up (or here) for an end-to-end smoke test.

Open questions / follow-ups

• @metamask/connect-multichain is at 1.1.0; confirm the solana_signTransaction
  return shape against the installed version if it bumps.
• Persistent-session re-hydration on reload (wallet_sessionChanged) is intentionally
  left to SwapKit's reconnect layer rather than the connector.
• Optional: expose headless / onDisplayUri passthrough so the widget can render its
  own QR instead of MetaMask's built-in modal.