fix(chat): actually promote workflow-chat attachments

Two reasons a workflow-chat image resolved to nothing, both silent:

The promotion ran under `if not chat_response.is_bot`, but that field defaults
to True, so the user's own question — the only message this was meant for —
was the one case it skipped. Keyed on the category instead.

And it looked for the upload link under `filepath`/`file_path` only, while
workflow chat carries it as `file_url`, so even when it did run there was
nothing to copy. All three spellings are accepted now.

Refs: features/v2.6.0/043-chat-file-permanent-storage

src/backend/bisheng/core/storage/chat_attachment.py

@@ -81,7 +81,10 @@ def _plan_promotions(files: list[dict], user_id: int | str, tmp_bucket: str) ->
         if not isinstance(file, dict) or file.get("object_name"):
             # Already permanent — task-mode uploads land in the main bucket.
             continue
-        source_object = temp_object_name_from_url(file.get("filepath") or file.get("file_path") or "", tmp_bucket)
+        # The upload endpoints disagree on the field name for the link they
+        # issued -- daily/task say filepath, workflow chat says file_url.
+        source_url = file.get("filepath") or file.get("file_path") or file.get("file_url") or ""
+        source_object = temp_object_name_from_url(source_url, tmp_bucket)
         if not source_object:
             continue
         dest_object = build_chat_object_name(user_id, file.get("filename") or file.get("file_name") or "")

src/backend/bisheng/worker/workflow/redis_callback.py

@@ -536,7 +536,9 @@ class RedisCallback(BaseCallback):
         # Attachments the user sent become permanent here, not at upload time —
         # uploads sit in the temp bucket, which clears itself every 3 days.
         # Only the user's own files: what the workflow produced is out of scope.
-        if not chat_response.is_bot:
+        # Keyed on category, not is_bot: that field defaults to True, so a
+        # question would have been skipped.
+        if chat_response.category == "question":
             promote_chat_attachments_sync(chat_response.files, self.user_id)
 
         message = ChatMessageDao.insert_one(

src/backend/test/core/test_promote_chat_attachments.py

@@ -67,6 +67,16 @@ class TestPromoteChatAttachments:
         assert "object_name" not in promoted[0]  # stays unresolvable, flagged to the user later
         assert promoted[1]["object_name"].startswith(f"{CHAT_OBJECT_PREFIX}7/")
 
+    async def test_workflow_chat_names_the_link_file_url(self, storage):
+        # Each upload path spells the link field differently; workflow chat says
+        # file_url, and reading only `filepath` silently promoted nothing.
+        files = [{"file_id": "f1", "file_name": "a.png", "file_url": "/bisheng-tmp/abc.png"}]
+
+        promoted = await promote_chat_attachments(files, user_id=7)
+
+        storage.copy_object.assert_awaited_once()
+        assert promoted[0]["object_name"].startswith(f"{CHAT_OBJECT_PREFIX}7/")
+
     async def test_extension_is_carried_over_from_the_display_name(self, storage):
         files = [{"file_id": "f1", "filename": "报告.PDF", "filepath": "/bisheng-tmp/xyz.pdf"}]