example(crm): add days_to_close formula using the new daysBetween stdlib fn

Demonstrates (and regression-covers, via the example build) the newly-registered
`daysBetween` — the canonical "days remaining" formula. Browser-verified: computes
+30/+60/… for open deals and negative for past closed_won dates.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: os-zhuang

examples/app-crm/src/objects/opportunity.object.ts

@@ -50,6 +50,12 @@ export const Opportunity = ObjectSchema.create({
     close_date: Field.date({
       label: 'Close Date',
     }),
+    // Exercises the newly-registered `daysBetween` stdlib function — the canonical
+    // "days remaining" formula (negative once the close date has passed).
+    days_to_close: Field.formula({
+      label: 'Days to Close',
+      expression: cel`record.close_date == null ? 0 : daysBetween(today(), record.close_date)`,
+    }),
     discount_percent: Field.percent({
       label: 'Discount %',
       defaultValue: 0,