Add centralized error handling with UI toast for user-facing errors

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

static/script.js

@@ -26,6 +26,17 @@
 const DEBUG = false;
 function debugLog(...args) { if (DEBUG) console.log(...args); }
 
+function handleError(context, error, showUI = false) {
+    console.error(`[${context}]`, error);
+    if (showUI) {
+        const msg = document.createElement('div');
+        msg.className = 'error-toast';
+        msg.textContent = `${context}: ${error.message || 'Unknown error'}`;
+        document.body.appendChild(msg);
+        setTimeout(() => msg.remove(), GLOW_DURATION_MS);
+    }
+}
+
 /* ---------- DOM references --------------------------------------- */
 const wrap         = document.getElementById('mapContainer');
 const group        = document.getElementById('mapGroup');
@@ -574,7 +585,7 @@ async function fetchHeatmapData() {
     debugLog(`Loaded ${heatmapData.length} heat map points from last ${data.hours_window} hours`);
     renderHeatmap();
   } catch (err) {
-    console.error('Failed to fetch heat map data:', err);
+    handleError('Heatmap', err);
   }
 }
 
@@ -659,7 +670,7 @@ async function fetchPortalData() {
     debugLog(`Loaded ${portalData.length} portals from last hour`);
     renderPortals();
   } catch (err) {
-    console.error('Failed to fetch portal data:', err);
+    handleError('Portals', err);
   }
 }
 
@@ -1057,8 +1068,8 @@ function showInventoryWindow(name) {
       invContent.appendChild(count);
     })
     .catch(err => {
+      handleError('Inventory', err, true);
       loading.textContent = `Failed to load inventory: ${err.message}`;
-      console.error('Inventory fetch failed:', err);
     });
 
   debugLog('Inventory window created for:', name);
@@ -1365,7 +1376,7 @@ async function pollLive() {
     renderTrails(trails);
     renderList();
   } catch (e) {
-    console.error('Live or trails fetch failed:', e);
+    handleError('Player update', e);
   }
 }
 
@@ -1375,7 +1386,7 @@ async function pollTotalRares() {
     const data = await response.json();
     updateTotalRaresDisplay(data);
   } catch (e) {
-    console.error('Total rares fetch failed:', e);
+    handleError('Rare counter', e);
   }
 }
 
@@ -1394,7 +1405,7 @@ async function pollTotalKills() {
     const data = await response.json();
     updateTotalKillsDisplay(data);
   } catch (e) {
-    console.error('Total kills fetch failed:', e);
+    handleError('Kill counter', e);
   }
 }
 
@@ -1411,7 +1422,7 @@ async function pollServerHealth() {
     const data = await response.json();
     updateServerStatusDisplay(data);
   } catch (e) {
-    console.error('Server health fetch failed:', e);
+    handleError('Server health', e);
     updateServerStatusDisplay({ status: 'error' });
   }
 }
@@ -1835,7 +1846,7 @@ function initWebSocket() {
     }
   });
   socket.addEventListener('close', () => setTimeout(initWebSocket, 2000));
-  socket.addEventListener('error', e => console.error('WebSocket error:', e));
+  socket.addEventListener('error', e => handleError('WebSocket', e));
 }
 
 // Display or create a chat window for a character