feat(agent): persist RAG and PlayBook trust receipts

apps/api/src/services/knowledge_service.py

@@ -680,18 +680,44 @@ class KnowledgeService:
 
     async def _embed_entry(self, entry_id: str, title: str, content: str) -> None:
         """背景任務：產生並儲存 embedding"""
+        await self.ensure_entry_embedding(
+            entry_id,
+            title,
+            content,
+        )
+
+    async def ensure_entry_embedding(
+        self,
+        entry_id: str,
+        title: str,
+        content: str,
+        *,
+        project_id: str | None = None,
+    ) -> bool:
+        """Synchronously persist and acknowledge one KM embedding."""
+
         try:
-            text = f"search_document: {title}\n\n{content[:2000]}"
-            embedding = await self._embed_svc.embed_text(text)
+            document = f"search_document: {title}\n\n{content[:2000]}"
+            embedding = await self._embed_svc.embed_text(document)
             if not embedding:
                 logger.warning("knowledge_embedding_empty", entry_id=entry_id)
-                return
-            async with get_db_context() as db:
+                return False
+            context = (
+                get_db_context(project_id)
+                if project_id is not None
+                else get_db_context()
+            )
+            async with context as db:
                 repo = KnowledgeDBRepository(db)
-                await repo.save_embedding(entry_id, embedding)
+                saved = await repo.save_embedding(entry_id, embedding)
+            if not saved:
+                logger.warning("knowledge_embedding_not_saved", entry_id=entry_id)
+                return False
             logger.info("knowledge_embedding_saved", entry_id=entry_id)
+            return True
         except Exception as e:
             logger.warning("knowledge_embedding_failed", entry_id=entry_id, error=str(e))
+            return False
 
     async def get_entry(self, entry_id: str) -> KnowledgeEntry | None:
         """取得知識條目 (view_count +1)"""