fix(web): stop reconnecting after explicit disconnect

[fallintoplace]

What changed

disconnect() used to close the socket and then let its close handler schedule a reconnect.

• stop reconnecting after an explicit disconnect
• clear and reset a cancelled reconnect timer
• ignore callbacks from sockets that are no longer active
• allow a later explicit connect() to enable reconnects again

Tests

• npm test
• changed-file ESLint
• npm run build