fix: prevent duplicate user message on session recovery re-publish

The re-published last user message was persisted into session history a
second time when the agent loop processed it, duplicating the user's
input. Mark the re-published InboundMessage with SKIP_USER_PERSIST_META
so should_persist_user_message() and _save_skip_for_turn() treat it as
already-persisted.

nanobot/agent/loop.py

@@ -2151,6 +2151,12 @@ class AgentLoop:
                             sender_id=chat_id,
                             chat_id=chat_id,
                             content=last_user_msg["content"],
+                            # The message already exists in session history
+                            # (persisted before the crash); skip persisting it
+                            # again so recovery does not duplicate it.
+                            metadata={
+                                turn_continuation.SKIP_USER_PERSIST_META: True
+                            },
                         )
                     )
                     logger.info(