chore(knowledge): 每次沉淀必打入口/结果日志，便于确认是否触发

success 路径原先完全静默，导致"看不到日志"无法区分"没触发"还是"日志不可见"。
现在每次 capture_thread 至少打 [knowledge] capturing… + 结果/跳过/失败 各一行。

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

offline-backend-20260512/backend/packages/harness/deerflow/knowledge/service.py

@@ -228,11 +228,22 @@ class KnowledgeService:
         Returns ``{"note": <note>, "created": bool}``. Raises
         :class:`EmptyThreadError` when there is nothing worth keeping.
         """
+        # Always-on entry log: proves a capture was triggered for this thread,
+        # regardless of how it ends (success / skip / fallback). Lets you tell
+        # "capture never ran" apart from "logs not visible" via one grep.
+        logger.info(
+            "[knowledge] capturing thread %s (msgs=%d, llm_extract=%s, skip_existing=%s)",
+            thread_id,
+            len(messages or []),
+            self.config.llm_extract_enabled,
+            skip_existing,
+        )
         if skip_existing:
             existing = await self.repo.find_by_source("thread", thread_id)
             if existing is None and self.adapter.manifest.has_source(f"thread:{thread_id}"):
                 existing = await self.repo.find_by_source("thread", thread_id)
             if existing:
+                logger.info("[knowledge] thread %s already captured (note %s); skipping", thread_id, existing.get("id"))
                 return {"note": existing, "created": False}
 
         sources = []
@@ -286,6 +297,7 @@ class KnowledgeService:
             )
             drafts = [single] if single else []
         if not drafts:
+            logger.info("[knowledge] thread %s has no sediment-able content; skipping", thread_id)
             raise EmptyThreadError(f"Thread {thread_id} has no sediment-able content")
 
         # When the LLM was enabled but silently fell back to rule-based extraction,
@@ -318,6 +330,14 @@ class KnowledgeService:
                     draft.related = list(dict.fromkeys([*siblings, *draft.related]))
 
         notes = [await self._persist_draft(draft, created_by=created_by) for draft in drafts]
+        logger.info(
+            "[knowledge] thread %s captured → %d note(s) [%s], status=%s, llm_fallback=%s",
+            thread_id,
+            len(notes),
+            ", ".join(n.get("title", "") for n in notes),
+            normalized,
+            llm_fallback,
+        )
         return {"note": notes[0], "created": True, "notes": notes, "llm_fallback": llm_fallback}
 
     async def capture_search(