fix(parser): prevent regex collision where /sale/i matched ACOS column instead of attributed sales

The generic regex /sale/i in ads column detection was matching "Advertising Cost
of Sales" (the ACOS % column) before reaching "7 day total sales" (the actual
attributed sales amount). This caused attributedSales30d to receive the ACOS
percentage instead of the real sales value, making experiment ACOS = 0 or 100%.

- Replace /sale/i with specific regexes: /\d+\s*day.*sale/i, /total\s+sale/i, etc.
- Replace /cost/i with regexes that exclude "cost of sales" columns
- Replace /unit/i with specific regexes for unit columns
- Add diagnostic logging for ads Excel column headers and first-row values
- Revert ACOS 100% fallback (root cause now fixed)

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

services/experimentAnalysis.ts

@@ -110,7 +110,7 @@ function getMetricValue(w: ComputedWeeklyMetrics, metric: string): number {
     case 'ctr': return w.ctr;
     case 'roas': return w.roas;
     case 'revenue': return w.revenue;
-    case 'acos': return w.cost > 0 ? (w.adRevenue > 0 ? (w.cost / w.adRevenue) * 100 : 100) : 0;
+    case 'acos': return w.cost > 0 && w.adRevenue > 0 ? (w.cost / w.adRevenue) * 100 : 0;
     default: return w.units;
   }
 }
@@ -173,8 +173,7 @@ function avgMetric(data: ComputedWeeklyMetrics[], metric: string, durationWeeks:
   if (metric === 'acos') {
     const totalAdRevenue = data.reduce((s, w) => s + w.adRevenue, 0);
     const totalCost = data.reduce((s, w) => s + w.cost, 0);
-    if (totalCost === 0) return 0; // No ad spend → ACOS is 0
-    return totalAdRevenue > 0 ? (totalCost / totalAdRevenue) * 100 : 100; // Cost but no ad revenue → 100% ACOS
+    return totalAdRevenue > 0 && totalCost > 0 ? (totalCost / totalAdRevenue) * 100 : 0;
   }
 
   // For absolute quantities (units, revenue, sessions), we sum them and divide by the duration