fix(compaction): harden continuation directive markers

src/shared/internal-initiator-marker.ts

@@ -1,11 +1,18 @@
 export const OMO_INTERNAL_INITIATOR_MARKER = "<!-- OMO_INTERNAL_INITIATOR -->"
 
+const INTERNAL_INITIATOR_MARKER_PATTERN = /\n*<!--\s*OMO_INTERNAL_INITIATOR\s*-->\s*/g
+
+export function stripInternalInitiatorMarkers(text: string): string {
+  return text.replace(INTERNAL_INITIATOR_MARKER_PATTERN, "").trimEnd()
+}
+
 export function createInternalAgentTextPart(text: string): {
   type: "text"
   text: string
 } {
+  const cleanText = stripInternalInitiatorMarkers(text)
   return {
     type: "text",
-    text: `${text}\n${OMO_INTERNAL_INITIATOR_MARKER}`,
+    text: `${cleanText}\n${OMO_INTERNAL_INITIATOR_MARKER}`,
   }
 }