Use descriptive names when multiple models would share the same chart label

After assigning short labels, detect duplicates (e.g. multiple
'Original' entries) and replace them with the model's full short name
for clarity.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

app.js

@@ -195,6 +195,18 @@ function assignModelColors() {
             MODEL_SHORT[model] = suffix || (isExternalModel(model) ? "Original" : name);
         });
     });
+    // Resolve duplicate short labels: use the model's short name instead
+    const labelCounts = {};
+    for (const m of ALL_MODELS) {
+        const lbl = MODEL_SHORT[m];
+        if (!labelCounts[lbl]) labelCounts[lbl] = [];
+        labelCounts[lbl].push(m);
+    }
+    for (const [lbl, models] of Object.entries(labelCounts)) {
+        if (models.length > 1) {
+            models.forEach(m => { MODEL_SHORT[m] = m.split("/").pop(); });
+        }
+    }
 }
 
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