Add real-time radar feature for nearby objects

Browser can open a radar window per character that streams nearby
monsters, players, NPCs, portals, and other objects in real-time.
On-demand activation via start_radar/stop_radar commands through
the existing WebSocket command channel.

- Backend: nearby_objects event handler with in-memory cache and broadcast
- Frontend: canvas mini-map + entity list table in draggable window
- Radar button added to player list alongside Chat/Stats/Inventory/Char

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

static/style.css

@@ -525,7 +525,7 @@ body {
   margin-top: 4px;
 }
 
-.chat-window, .stats-window, .inventory-window, .character-window {
+.chat-window, .stats-window, .inventory-window, .character-window, .radar-window {
   position: absolute;
   top: 10px;
   /* position window to start just right of the sidebar */
@@ -2502,3 +2502,131 @@ table.ts-allegiance td:first-child {
   border-top: 1px solid #5a4a24;
   border-bottom: 1px solid #5a4a24;
 }
+
+/* ─── Radar Window ─── */
+
+.radar-window {
+  width: 360px;
+  height: 560px;
+}
+
+.radar-window .window-content {
+  display: flex;
+  flex-direction: column;
+  overflow: hidden;
+}
+
+.radar-controls {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  padding: 4px 8px;
+  background: #1a1a1a;
+  border-bottom: 1px solid #333;
+  font-size: 0.8rem;
+}
+
+.radar-controls label {
+  display: flex;
+  align-items: center;
+  gap: 4px;
+  color: #ccc;
+}
+
+.radar-range-select {
+  background: #222;
+  color: #ccc;
+  border: 1px solid #444;
+  padding: 2px 4px;
+  font-size: 0.75rem;
+}
+
+.radar-canvas {
+  display: block;
+  margin: 0 auto;
+  border-bottom: 1px solid #333;
+  flex-shrink: 0;
+}
+
+.radar-entity-list {
+  flex: 1;
+  overflow-y: auto;
+  font-size: 0.75rem;
+  min-height: 0;
+}
+
+.radar-entity-header,
+.radar-entity-row {
+  display: flex;
+  align-items: center;
+  padding: 2px 6px;
+  gap: 4px;
+}
+
+.radar-entity-header {
+  background: #1a1a1a;
+  color: #888;
+  font-weight: bold;
+  border-bottom: 1px solid #333;
+  position: sticky;
+  top: 0;
+}
+
+.radar-entity-row {
+  border-bottom: 1px solid #222;
+}
+
+.radar-entity-row:hover {
+  background: #1a1a2a;
+}
+
+.re-color {
+  width: 8px;
+  height: 8px;
+  border-radius: 50%;
+  flex-shrink: 0;
+  display: inline-block;
+}
+
+.re-name {
+  flex: 1;
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  color: #ddd;
+}
+
+.re-type {
+  width: 60px;
+  flex-shrink: 0;
+  color: #888;
+}
+
+.re-dist {
+  width: 45px;
+  flex-shrink: 0;
+  text-align: right;
+  color: #aaa;
+}
+
+.re-dir {
+  width: 24px;
+  flex-shrink: 0;
+  text-align: center;
+  color: #888;
+}
+
+.radar-btn {
+  background: #553388;
+  color: #fff;
+  border: 1px solid #774499;
+  padding: 1px 6px;
+  cursor: pointer;
+  font-size: 0.7rem;
+  border-radius: 3px;
+}
+
+.radar-btn:hover {
+  background: #664499;
+}