fix(connect-multichain): clean up MWP session on connection rejection

[adonesky1]

Summary

• Fix stale MWP session persisting in KVStore after user rejects a QR code connection in the wallet, which prevented subsequent connection attempts

Problem

When connecting via QR code, the MWP handshake completes and stores a session:{id} entry in the KVStore before the wallet responds to wallet_createSession. If the user then rejects the connection in the wallet:

1. rejectConnection() is called in initialConnectionMessageHandler, but dappClient.disconnect() is never called
2. dappClient.disconnect() is the only method that calls sessionstore.delete(session.id) to remove the session from the KVStore
3. The stale session remains in storage indefinitely
4. On the next connection attempt, getActiveSession() finds this stale session and enters the resume branch — trying to resume a session the wallet already rejected
5. The resume either hangs or times out, blocking the user from connecting

Fix

Call dappClient.disconnect() in MWPTransport.connect()'s catch handler so that any connection failure (rejection, timeout, etc.) properly cleans up the dappClient session from the KVStore. The .catch(() => {}) on disconnect ensures cleanup errors don't mask the original connection error.

Test plan

• Initiate a QR code connection from the dapp
• Scan the QR code with the MetaMask wallet
• Reject the connection in the wallet
• Verify the rejection error propagates to the dapp
• Initiate a new QR code connection — it should show a fresh QR code and not hang/timeout
• Accept the second connection and verify it completes successfully