show the average setup by default

app/src/content/embeds/d3-benchmark-comparison.html

@@ -11,6 +11,7 @@
     "setups":         { "Setup Label": { "datasets": {...} }, ... },        // optional, multi-setup mode with dropdown + average
     "defaultMetric":  "agg_score_macro",                                    // optional, default: "agg_score_macro"
     "defaultView":    "bar",                                                // optional, "bar" | "line", default: "bar"
+    "defaultSetup":   "average",                                            // optional, setup name or "average", default: "average" when ≥2 setups
     "tokensPerStep":  2100000,                                              // optional, default: 2.1e6
     "runColumn":      "runname",                                            // optional, CSV column for series, default: "runname"
     "stepColumn":     "steps"                                               // optional, CSV column for x-axis, default: "steps"
@@ -203,9 +204,10 @@
       // ─── SETUP SUPPORT ───
       const SETUPS = cfg.setups || null;
       const setupNames = SETUPS ? Object.keys(SETUPS) : [];
-      let currentSetup = SETUPS ? setupNames[0] : null;
-      let DATASETS = SETUPS ? normalizeDatasets(SETUPS[setupNames[0]].datasets) : normalizeDatasets(cfg.datasets);
       const AVG_SETUP_KEY = 'Average (all setups)';
+      const defaultSetupCfg = cfg.defaultSetup || (setupNames.length >= 2 ? 'average' : null);
+      let currentSetup = SETUPS ? (defaultSetupCfg === 'average' ? AVG_SETUP_KEY : (defaultSetupCfg && setupNames.includes(defaultSetupCfg) ? defaultSetupCfg : setupNames[0])) : null;
+      let DATASETS = SETUPS ? (currentSetup === AVG_SETUP_KEY ? {} : normalizeDatasets(SETUPS[currentSetup].datasets)) : normalizeDatasets(cfg.datasets);
       let avgDatasets = {};
       let parsedData = [];
 
@@ -712,6 +714,7 @@
           });
           if (setupNames.length >= 2) {
             const avgOpt = document.createElement('option'); avgOpt.value = AVG_SETUP_KEY; avgOpt.textContent = AVG_SETUP_KEY;
+            if (currentSetup === AVG_SETUP_KEY) avgOpt.selected = true;
             setupSelect.appendChild(avgOpt);
           }
           setupSelect.addEventListener('change', () => { switchSetup(setupSelect.value); });
@@ -824,6 +827,7 @@
             avgDatasets = avg.datasets;
             parsedData = parsed.concat(avg.data);
             parsedData.columns = parsed.columns;
+            if (currentSetup === AVG_SETUP_KEY) DATASETS = { ...avgDatasets };
           }
           filterData();
           metricKeys = detectMetrics(allData.columns);