docs: NixOS deployment guide from Camellia

This reverts commit ded5d4d8ed.

nanobot/agent/loop.py

@@ -378,7 +378,6 @@ class AgentLoop:
         )
         self._unified_session = unified_session
         self._running = False
-        self._shutting_down = False
         self._mcp_servers = mcp_servers or {}
         self._mcp_stacks: dict[str, MCPConnection] = {}
         self._mcp_connecting = False
@@ -1225,11 +1224,11 @@ class AgentLoop:
                     # it into session history now makes it visible in the
                     # next conversation turn.
                     #
-                    # During gateway shutdown (self._shutting_down is True),
+                    # During gateway shutdown (self._running is False), skip
-                    # skip this so the pending markers survive and
+                    # this so the pending markers survive and
                     # recover_stale_sessions() can notify the user and
                     # re-trigger the interrupted turn on next startup.
-                    if not self._shutting_down:
+                    if self._running:
                         try:
                             key = self._effective_session_key(msg)
                             session = self.sessions.get_or_create(key)
@@ -1319,7 +1318,6 @@ class AgentLoop:
     def stop(self) -> None:
         """Stop the agent loop."""
         self._running = False
-        self._shutting_down = True
         logger.info("Agent loop stopping")
 
     async def _process_message(
@@ -2153,12 +2151,6 @@ 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(