feat(protocol2): presence stream — online population + region transitions (Part B ph.2)

Overlay BridgePresence (new):
- presence.online sweep over online PlayerMobiles: total plus per-facet and
  per-region counts, emitted only when the population changes.
- region.enter real-time from EventSink.OnEnterRegion (player-filtered), the
  cheap location signal PLAN.md prefers over Movement.
- PresenceSweepSeconds (30s); wired into [bridge reload|sweepnow|status.

Sidecar:
- GET /online serves the latest presence.online snapshot from the event store
  (survives restart); population time series via /history?kind=presence.online.

Docs: INTEGRATION.md presence events + /online endpoint; PROTOCOL_2 ph.2 built.

Verified: sidecar cargo check clean; overlay compiles in the full ServUO
Scripts tree (0 errors, 0 warnings). Live run pending.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

overlay/Scripts/Custom/Bridge/BridgeConfig.cs

@@ -33,6 +33,8 @@ namespace Server.Custom.Bridge
         public static int ChampSweepSeconds { get; private set; }
         public static int GuildSweepSeconds { get; private set; }
         public static int CitySweepSeconds { get; private set; }
+        public static int PresenceSweepSeconds { get; private set; }
+        public static int HousingSweepSeconds { get; private set; }
 
         public static string LinkUrl { get; private set; }
 
@@ -91,6 +93,14 @@ namespace Server.Custom.Bridge
             if (CitySweepSeconds < 1)
                 CitySweepSeconds = 1;
 
+            PresenceSweepSeconds = Config.Get("Bridge.PresenceSweepSeconds", 30);
+            if (PresenceSweepSeconds < 1)
+                PresenceSweepSeconds = 1;
+
+            HousingSweepSeconds = Config.Get("Bridge.HousingSweepSeconds", 300);
+            if (HousingSweepSeconds < 1)
+                HousingSweepSeconds = 1;
+
             LinkUrl = Config.Get("Bridge.LinkUrl", "https://yoursite/link");
 
             TownCrierMaxLines = Config.Get("Bridge.TownCrierMaxLines", 6);