Add cascading fallback for deal titles instead of hardcoded "Unknown"

Replace the simple nil-title → "Unknown" logic in printDeal with a
fallbackDealTitle() function that tries multiple fields in priority
order before giving up:

  1. Title (cleaned) — the happy path, same as before
  2. Brand + Department — e.g. "Publix deal (Meat)"
  3. Brand alone — e.g. "Publix deal"
  4. Department alone — e.g. "Meat deal"
  5. Description truncated to 48 chars — last-resort meaningful text
  6. Item ID — e.g. "Deal 12345"
  7. "Untitled deal" — only when every field is empty

This makes the output more useful for the ~5-10% of weekly ad items
that ship with a nil Title from the Publix API, which previously all
showed as "Unknown" and were indistinguishable from each other.

Tests:
- TestPrintDeals_FallbackTitleFromBrandAndDepartment
- TestPrintDeals_FallbackTitleFromID

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

internal/display/formatter.go

@@ -151,10 +151,7 @@ func PrintWarning(w io.Writer, msg string) {
 }
 
 func printDeal(w io.Writer, item api.SavingItem) {
-	title := filter.CleanText(filter.Deref(item.Title))
-	if title == "" {
-		title = "Unknown"
-	}
+	title := fallbackDealTitle(item)
 	savings := filter.CleanText(filter.Deref(item.Savings))
 	desc := filter.CleanText(filter.Deref(item.Description))
 	dept := filter.CleanText(filter.Deref(item.Department))
@@ -198,6 +195,37 @@ func printDeal(w io.Writer, item api.SavingItem) {
 	}
 }
 
+func fallbackDealTitle(item api.SavingItem) string {
+	if title := filter.CleanText(filter.Deref(item.Title)); title != "" {
+		return title
+	}
+
+	brand := filter.CleanText(filter.Deref(item.Brand))
+	dept := filter.CleanText(filter.Deref(item.Department))
+	switch {
+	case brand != "" && dept != "":
+		return fmt.Sprintf("%s deal (%s)", brand, dept)
+	case brand != "":
+		return brand + " deal"
+	case dept != "":
+		return dept + " deal"
+	}
+
+	if desc := filter.CleanText(filter.Deref(item.Description)); desc != "" {
+		const max = 48
+		if len(desc) > max {
+			return desc[:max-3] + "..."
+		}
+		return desc
+	}
+
+	if item.ID != "" {
+		return "Deal " + item.ID
+	}
+
+	return "Untitled deal"
+}
+
 func toDealJSON(item api.SavingItem) DealJSON {
 	categories := item.Categories
 	if categories == nil {