feat: increase turn timeout to 10s and expand help screen

- Turn timeout 5s → 10s for more comfortable gameplay
- Help screen now covers: lobby, exploration, combat, shop, classes,
  multiplayer tips, and general tips including skill tree controls

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

game/session_test.go

@@ -63,8 +63,8 @@ func TestSessionTurnTimeout(t *testing.T) {
 	select {
 	case <-done:
 		// Turn completed via timeout
-	case <-time.After(7 * time.Second):
-		t.Error("Turn did not timeout within 7 seconds")
+	case <-time.After(12 * time.Second):
+		t.Error("Turn did not timeout within 12 seconds")
 	}
 }