feat(bridge): publish the player-vendor market index as vendor.listing

Protocol 3.0 §8. Every player vendor's shop name, owner, location and priced
inventory, so the website can offer the search the in-game Vendor Search gump
offers — from outside the game, and honouring the same per-player opt-out.

It cannot be an RPC. rpc.rs correlates a reply on the FIRST frame carrying a
matching reqId, so a chunked reply sharing one reqId would deliver chunk 1 to the
HTTP caller and leak chunks 2..N onto the broadcast feed; a whole-world snapshot
would not fit in one frame inside the 10 s timeout either. So it is a diff sweep
on the broadcast stream, one authoritative frame per vendor.

The one genuinely new pattern here is an amortized round-robin: every other sweep
walks its whole collection per tick, which is fine for tens of houses and is not
fine for a world of shops whose inventories recurse into containers.
MarketSweepBatch (25) vendors are inventoried per tick from a persistent cursor,
so per-tick cost is bounded by the batch rather than by world size.

VendorSearch.GetItemName is never called: it builds an ObjectPropertyList,
serialises it and byte-parses the packet per item. The frame carries itemId, hue,
amount, price, the plain item.Name field and item.LabelNumber; the website
resolves names against its own cliloc table. (It would not work anyway — every
current client ships its cliloc files compressed and ServUO's Ultima.StringList
cannot read them, so the in-game gump has the same gap.)

Measured on the live shard (27 vendors x 40 listings, 209k items / 43k mobiles):
15.4 ms for the first cold tick of 25 vendors, 3.4 ms for the next, 0.3 ms in
steady state. `[bridge status` now reports lastMs/maxMs and a tick over 50 ms
warns, naming the knob — the batch cap is a claim about that number and an
operator tuning it was otherwise tuning blind.

- location is ONE nested object, not flat map/x/y/region, so the website's single
  market.location visibility rule can hide a vendor's whereabouts on both the
  live frame and the stored read model. Flat keys would need five rules.
- Owner is flat ownerSerial/ownerName, never BridgeJson.Actor, which would add
  acct and webId. Same argument points.board makes.
- pv.VendorSearch is honoured, so a shop hidden in game is hidden on the site;
  the seen-set removal then emits vendor.listing.remove.
- Container-priced items carry child:true, exactly as DoSearch reports them.
- Over MarketMaxListings (250) the frame says truncated and carries the real
  total, so the site shows "250 of 3,104" rather than a partial shop as complete.

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

overlay/Scripts/Custom/Bridge/BridgeConfig.cs

@@ -36,6 +36,12 @@ namespace Server.Custom.Bridge
         public static int PresenceSweepSeconds { get; private set; }
         public static int HousingSweepSeconds { get; private set; }
         public static int PointsSweepSeconds { get; private set; }
+        public static int MarketSweepSeconds { get; private set; }
+
+        // ---- player-vendor market index (https://gitea.whitlocktech.com/RunicGateway/docs/src/branch/main/link/v3.md §8) ----
+        public static bool MarketEnabled { get; private set; }
+        public static int MarketSweepBatch { get; private set; }
+        public static int MarketMaxListings { get; private set; }
 
         // ---- points / loyalty leaderboards (https://gitea.whitlocktech.com/RunicGateway/docs/src/branch/main/link/v3.md §7) ----
         public static bool PointsLeaderboardEnabled { get; private set; }
@@ -149,6 +155,36 @@ namespace Server.Custom.Bridge
             // on every profile build. See BridgeProfile.WritePoints.
             PointsProfileRank = Config.Get("Bridge.PointsProfileRank", false);
 
+            // Player-vendor market index. Unlike every other sweep, this one does NOT walk its whole
+            // collection per tick: MarketSweepBatch caps how many vendors are inventoried, and a
+            // persistent cursor round-robins through the rest, so the per-tick cost is bounded by
+            // the batch rather than by how many vendors the world holds.
+            MarketEnabled = Config.Get("Bridge.MarketEnabled", true);
+
+            MarketSweepSeconds = Config.Get("Bridge.MarketSweepSeconds", 60);
+            if (MarketSweepSeconds < 1)
+                MarketSweepSeconds = 1;
+
+            // Bounded below at 1 (a batch of 0 would advance the cursor nowhere and publish nothing,
+            // silently) and above at 500, past which the batch stops bounding anything on any
+            // realistic shard and the tick is a whole-world pass by another name.
+            MarketSweepBatch = Config.Get("Bridge.MarketSweepBatch", 25);
+            if (MarketSweepBatch < 1)
+                MarketSweepBatch = 1;
+            if (MarketSweepBatch > 500)
+                MarketSweepBatch = 500;
+
+            // Per-vendor listing cap. BridgeJson.Parse caps INBOUND frames at 1 MB; outbound is
+            // uncapped and the sidecar's read_line will allocate whatever arrives, so the cap here
+            // is what keeps one commodity reseller with 8,000 stacked resources from emitting a
+            // multi-megabyte frame. Over the cap the frame carries "truncated": true and the site
+            // says so.
+            MarketMaxListings = Config.Get("Bridge.MarketMaxListings", 250);
+            if (MarketMaxListings < 1)
+                MarketMaxListings = 1;
+            if (MarketMaxListings > 5000)
+                MarketMaxListings = 5000;
+
             // The ruleset frame is not a sweep — it is emitted once per sidecar connect (and on
             // `[bridge reload`), so it has no interval. PublicConnectAddress is the ONE connection
             // detail the bridge will publish, and only because an operator typed it here for that