5b2: make the pipe escape terminate, cap the value a document fault echoes

src/adf/document.ts

@@ -90,7 +90,8 @@ function isRecord(value: unknown): value is Record<string, unknown> {
 }
 
 function describe(value: unknown): string {
-  if (typeof value === 'string') return JSON.stringify(value)
+  if (typeof value === 'string') return JSON.stringify(value.length > 40 ? `${value.slice(0, 40)}…` : value)
+  if (typeof value === 'function') return 'a function'
   if (typeof value === 'object' && value !== null) return Array.isArray(value) ? 'an array' : 'an object'
   return String(value)
 }