There were two identity systems: SessionManager keyed on the stable, UNIQUE
anon_token, and getOrCreateUser keyed on the mutable, non-unique socket_id.
The latter could create a duplicate "orphan" user row (or resolve the wrong
row) when the socket_id lookup raced the session's socket_id update —
desyncing credits and payouts between the two rows for one human.
- getOrCreateUser now resolves through SessionManager's stable identity first
(anon_token -> users.id), re-selecting a fresh row by stable id, and only
falls back to the legacy socket_id lookup when no session exists. The
last-resort create now warns, since it indicates a missing session.
- gameModeManager.sessionManager is wired in SocketHandlers so the
session-first path is active in production.
- anon_token is already UNIQUE (migration 003), so the stable-identity
constraint already exists; no new migration needed.
Re-keying the in-memory activeGames map by user_id is deferred (invasive;
already mitigated by stamping dbUserId on the game in the disconnect fix).
Adds identityResolution.test.js proving no duplicate row is created when a
session exists. Full suite: 17 suites / 136 tests.
