fix: deterministic multi-GPX trackpoint ordering and catch-path completion

Pre-allocate fileResults[idx] slots so GPX files always concatenate in URL
order regardless of fetch arrival order (Bug 1). Both .then and .catch now
call computeDistance() after decrementing pending so a failed last fetch no
longer leaves the distance element permanently blank (Bug 2).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WPJztrVGbwic2xTG7G9fjM

themes/intotheeast/templates/stats.html.twig

@@ -144,23 +144,39 @@ function haversine(lat1, lng1, lat2, lng2) {
 var distEl = document.getElementById('stat-distance');
 
 if (GPX_URLS.length > 0) {
-    // Mode A: sum haversine between all GPX trackpoints
+    // Mode A: sum haversine between all GPX trackpoints (deterministic order)
     var pending = GPX_URLS.length;
-    var masterPts = [];
-    GPX_URLS.forEach(function(url) {
+    var fileResults = new Array(GPX_URLS.length);
+    GPX_URLS.forEach(function(url, idx) {
         fetch(url)
             .then(function(r) { return r.text(); })
             .then(function(text) {
                 var xml = new DOMParser().parseFromString(text, 'text/xml');
                 var trkpts = xml.querySelectorAll('trkpt');
+                var pts = [];
                 trkpts.forEach(function(pt) {
-                    masterPts.push({
+                    pts.push({
                         lat: parseFloat(pt.getAttribute('lat')),
                         lon: parseFloat(pt.getAttribute('lon'))
                     });
                 });
+                fileResults[idx] = pts;
                 pending--;
-                if (pending === 0) {
+                if (pending === 0) { computeDistance(); }
+            })
+            .catch(function(err) {
+                console.warn('GPX load failed:', url, err);
+                fileResults[idx] = [];
+                pending--;
+                if (pending === 0) { computeDistance(); }
+            });
+    });
+
+    function computeDistance() {
+        var masterPts = [];
+        fileResults.forEach(function(pts) {
+            if (pts) { pts.forEach(function(p) { masterPts.push(p); }); }
+        });
         var total = 0;
         for (var i = 1; i < masterPts.length; i++) {
             total += haversine(masterPts[i-1].lat, masterPts[i-1].lon,
@@ -168,9 +184,6 @@ if (GPX_URLS.length > 0) {
         }
         distEl.textContent = masterPts.length < 2 ? '—' : Math.round(total).toLocaleString();
     }
-            })
-            .catch(function(err) { console.warn('GPX load failed:', url, err); pending--; });
-    });
 } else {
     // Mode B: sum haversine between consecutive entry lat/lng points
     var total = 0;