Answer the stability pass: the slot a line ending reached, and the text an image description dropped

src/markdown/directive-syntax.ts

@@ -77,6 +77,12 @@ export function readInlineDirective(text: string, index: number): Read<Directive
   return readNestedDirective(text, index, 1)
 }
 
+// Both directions answer alike: an inline directive never spans lines, so no content slot holds a line ending.
+export function slotLineEndingFault(type: string, text: string): ConvertFault | undefined {
+  if (!/[\n\r]/.test(text)) return undefined
+  return { code: 'unspellable-whitespace', message: `the ${type} content slot holds a newline no inline directive spans` }
+}
+
 export function spellAttributes(pairs: readonly (readonly [string, string])[]): string {
   if (pairs.length === 0) return ''
   const spelled = [...pairs].sort(([left], [right]) => keyOrder(left, right)).map(([key, value]) => `${key}=${value}`)