add conversation expire config & user query text to dingtalk card (#2147)

* add conversation expire config

* add user query text to card

* fix(pipeline): move session limit to AI config

* test(pipeline): cover AI session limit config

* refactor(pipeline): merge session expire-time into AI runner stage

Move the session validity duration field out of the standalone
session-limit stage into the runner stage so it actually renders in the
AI tab (the tab only shows the runner stage and the stage matching the
selected runner — any other stage is filtered out). Read path, default
config, metadata description, and tests updated accordingly.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(pipeline): expire conversations from last update time

* fix(n8n): sync generated conversation id into payload

---------

Co-authored-by: RockChinQ <rockchinq@gmail.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/langbot/pkg/provider/runners/n8nsvapi.py

@@ -187,6 +187,12 @@ class N8nServiceAPIRunner(runner.RequestRunner):
         if not query.session.using_conversation.uuid:
             query.session.using_conversation.uuid = str(uuid.uuid4())
 
+        # Keep query variables in sync with the generated/new conversation id.
+        # query.variables is later merged into payload and would otherwise
+        # overwrite the generated conversation_id with the stale preprocessor
+        # value (usually None for a new conversation).
+        query.variables['conversation_id'] = query.session.using_conversation.uuid
+
         # 预处理用户消息
         plain_text = await self._preprocess_user_message(query)