fix: resume the Login on a reopened connection

[diegolmello]

Proposed changes

A Reopen builds a new connection, and the DDP session the previous Login belonged to is gone with the old one. Nothing logged in again on the new connection, so a reopened Socket carried no authenticated identity — closes #359.

onOpen now resumes the Login when a token is held. It fires after emit("open") and after the open resolves, and it is not awaited: the open path never waits on the Login, and a failure is logged rather than thrown into the websocket callback.

loggedIn was connected && !!resume. The token survives across connections and nothing clears it, so a reopened, anonymous session reported itself logged in. Authentication is now tracked per connection: set when login resolves, cleared when a connection is created, on close, and on logout. The token store is unchanged — it is what makes the resume possible.

Steps to reproduce

• Connect and log in.
• Drop the connection so the Socket schedules a Reopen.
• Once the new connection has handshaken, observe that no login method call goes out, while loggedIn reports true.

Tests

• a reopened connection with a held token sends one login method call carrying the resume token
• a reopened connection with no token held sends no login method call
• the open resolves and open is emitted without waiting on the login response
• loggedIn is false between the reopen and the login result, and true after it