Add player position tracking relay + rendering (Phase 7b)

Relays the mod's throttled player_positions roster over a new
/ws/players/:serverId gateway (Redis pub/sub + snapshot key so a
tab connecting between mod flushes isn't empty), gated per-server
by a new playerPositionsVisible admin toggle independent of the
mod's own tracking config. Frontend renders the roster as map
markers with a show/hide toggle and online count. Covered by unit
tests (players.test.ts, ws-gateway.test.ts, admin.test.ts) and a
new e2e spec that plays the real mod WS protocol from inside a
browser context.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015tKdPZt78zbPUZMXWzKEKt

frontend/src/public/js/admin.js

@@ -60,6 +60,7 @@ function adminpanel() {
           authMode: server.authMode,
           anonymousChatAllowed: server.anonymousChatAllowed,
           waypointFormat: server.waypointFormat,
+          playerPositionsVisible: server.playerPositionsVisible,
         }),
       });
       server.status = res.ok ? "saved" : "save failed";

frontend/src/public/js/map.js

@@ -18,6 +18,7 @@ const DEFAULT_MARKER_HEIGHT = 60;
 // api/src/link.ts's doc comment for why that's a deliberate Phase 3 MVP tradeoff.
 const SESSION_STORAGE_KEY = "mcmapper_session";
 const NICKNAME_STORAGE_KEY = "mcmapper_nickname";
+const SHOW_PLAYERS_STORAGE_KEY = "mcmapper_show_players";
 
 function mapmapper() {
   return {
@@ -55,6 +56,16 @@ function mapmapper() {
     regionStatus: "",
     exporting: false,
 
+    // Phase 7b: live player positions, relayed from the mod via /ws/players/:serverId (see
+    // players-gateway.ts). `onlinePlayers` always reflects the full current roster (not a diff,
+    // same "current state" philosophy as markers/columns) — a player logging out just stops
+    // appearing in the next message. `showPlayers` only toggles the map layer; the roster (and
+    // the sidebar count) keeps updating either way.
+    playersSocket: null,
+    playerLayer: null,
+    onlinePlayers: [],
+    showPlayers: localStorage.getItem(SHOW_PLAYERS_STORAGE_KEY) !== "false",
+
     async init() {
       const servers = await fetch("/api/servers").then((r) => r.json());
       this.loading = false;
@@ -63,6 +74,7 @@ function mapmapper() {
       this.leaflet = L.map("map", { crs: L.CRS.Simple, minZoom: -4, maxZoom: 6 });
       this.leaflet.setView([0, 0], 0);
       this.markerLayer = L.layerGroup().addTo(this.leaflet);
+      this.playerLayer = L.layerGroup().addTo(this.leaflet);
       this.leaflet.on("click", (e) => this.onMapClick(e));
       this.leaflet.on("mousedown", (e) => this.startRegionSelect(e));
 
@@ -87,6 +99,7 @@ function mapmapper() {
         await this.loadAccount();
         await this.loadMarkers();
         this.connectChat();
+        this.connectPlayers();
       }
     },
 
@@ -393,6 +406,37 @@ function mapmapper() {
       };
     },
 
+    connectPlayers() {
+      const proto = location.protocol === "https:" ? "wss" : "ws";
+      this.playersSocket = new WebSocket(`${proto}://${location.host}/ws/players/${this.server.id}`);
+      this.playersSocket.onmessage = (ev) => {
+        const { players } = JSON.parse(ev.data);
+        this.onlinePlayers = players;
+        this.renderPlayerLayer(players);
+      };
+    },
+
+    renderPlayerLayer(players) {
+      this.playerLayer.clearLayers();
+      if (!this.showPlayers) return;
+      for (const player of players) {
+        L.circleMarker(worldToLatLng(player.x, player.z), {
+          radius: 5,
+          color: "#facc15",
+          fillColor: "#facc15",
+          fillOpacity: 1,
+          weight: 2,
+        })
+          .bindTooltip(player.username, { permanent: true, direction: "top", offset: [0, -6] })
+          .addTo(this.playerLayer);
+      }
+    },
+
+    onShowPlayersChange() {
+      localStorage.setItem(SHOW_PLAYERS_STORAGE_KEY, String(this.showPlayers));
+      this.renderPlayerLayer(this.onlinePlayers);
+    },
+
     sendChat() {
       const message = this.chatInput.trim();
       if (!message || !this.chatSocket) return;