Fix cost per gram on inventory detail for discrete products

For discrete items, show "Cost per ct" using price/count instead of
dividing by countOriginal*unitWeight (which treated mg as grams for
edibles, showing $0.02 instead of $3.50).

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

web/src/components/ProductDetail.tsx

@@ -77,11 +77,11 @@ export function ProductDetail({
     ["Bin", isCheckedOut ? "In your custody" : bin ? bin.name : <span style={{ color: "var(--ink-3)" }}>—</span>],
     ["Audit cadence", `Every ${cfg?.cadenceDays ?? "—"} days · ${cfg?.auditMode ?? "—"}`],
     [
-      "Cost per gram",
+      item.kind === "discrete" ? `Cost per ${cfg?.unit ?? "ct"}` : "Cost per gram",
       item.kind === "bulk" && item.weight > 0
         ? fmt.money(item.price / item.weight)
-        : item.kind === "discrete" && item.unitWeight > 0
-          ? `${fmt.money(item.price / (item.countOriginal * item.unitWeight))} (effective)`
+        : item.kind === "discrete" && item.countOriginal > 0
+          ? fmt.money(item.price / item.countOriginal)
           : "—",
     ],
   ];