Phase 7: Typed event system + centralized timer manager - #2336

Session Architecture Redesign — Phase 7 of 8

What

Add type-safe event emitter, centralized timer management, and session lifecycle events.

New Files

• typed_event_emitter.ts: TypedEventEmitter<T> wrapping Node's EventEmitter with compile-time event name + payload type checking
• session_events.ts: SessionEvents interface — roundStart, roundEnd, stateChange, sessionEnd
• timer_manager.ts: TimerManager with named set()/clear()/setInterval()/clearInterval()/clearAll() — guarantees all timers cleaned on session end

Changes to Existing Files

session.ts:

• Added events (TypedEventEmitter) and timers (TimerManager) properties
• Replaced guessTimeoutFunc field with timers.set('guessTimeout', ...)
• stopGuessTimeout() → timers.clear('guessTimeout')
• endSession(): timers.clearAll(), emit sessionEnd, events.removeAllListeners()

game_session.ts:

• Removed hiddenUpdateTimer field
• startHiddenUpdateTimer() → timers.setInterval('hiddenUpdate', ...)
• stopHiddenUpdateTimer() → timers.clearInterval('hiddenUpdate')

Risk: Low

Existing timer behavior is preserved — just centralized under named slots. The clearAll() call in endSession() is the key safety improvement: no timer can survive past session teardown.

Stack Order

  Phase 1 — Foundation
  Phase 2 — Enforce state machine
  Phase 3 — Consolidate mutex
  Phase 4 — Voice manager extraction
  Phase 5 — Scoreboard hardening
  Phase 6 — Clean API surface
► Phase 7 (this PR) — Event system + timer manager (depends on Phase 1)
  Phase 8 — Registry replaces State maps

Race Conditions Addressed

• RACE-15: Guess timeout timer guaranteed cleanup on session end
• RACE-24: Hidden update interval guaranteed cleanup on session end
• Listener leak prevention via events.removeAllListeners() on dispose