fix(restart): preserve channel metadata across /restart so reply lands in thread

cmd_restart only persisted channel + chat_id across the os.execv boundary, so
when the new process announced "Restart completed" the OutboundMessage had
no Slack thread_ts and the reply fell back to the channel root.

Serialize msg.metadata into NANOBOT_RESTART_NOTIFY_METADATA, restore it on the
RestartNotice, and forward it to OutboundMessage so the completion message
follows the same routing as the original /restart invocation.

Made-with: Cursor

tests/utils/test_restart.py

@@ -16,6 +16,7 @@ from nanobot.utils.restart import (
 def test_set_and_consume_restart_notice_env_roundtrip(monkeypatch):
     monkeypatch.delenv("NANOBOT_RESTART_NOTIFY_CHANNEL", raising=False)
     monkeypatch.delenv("NANOBOT_RESTART_NOTIFY_CHAT_ID", raising=False)
+    monkeypatch.delenv("NANOBOT_RESTART_NOTIFY_METADATA", raising=False)
     monkeypatch.delenv("NANOBOT_RESTART_STARTED_AT", raising=False)
 
     set_restart_notice_to_env(channel="feishu", chat_id="oc_123")
@@ -25,14 +26,42 @@ def test_set_and_consume_restart_notice_env_roundtrip(monkeypatch):
     assert notice.channel == "feishu"
     assert notice.chat_id == "oc_123"
     assert notice.started_at_raw
+    assert notice.metadata == {}
 
     # Consumed values should be cleared from env.
     assert consume_restart_notice_from_env() is None
     assert "NANOBOT_RESTART_NOTIFY_CHANNEL" not in os.environ
     assert "NANOBOT_RESTART_NOTIFY_CHAT_ID" not in os.environ
+    assert "NANOBOT_RESTART_NOTIFY_METADATA" not in os.environ
     assert "NANOBOT_RESTART_STARTED_AT" not in os.environ
 
 
+def test_restart_notice_preserves_metadata_across_env(monkeypatch):
+    monkeypatch.delenv("NANOBOT_RESTART_NOTIFY_CHANNEL", raising=False)
+    monkeypatch.delenv("NANOBOT_RESTART_NOTIFY_CHAT_ID", raising=False)
+    monkeypatch.delenv("NANOBOT_RESTART_NOTIFY_METADATA", raising=False)
+    monkeypatch.delenv("NANOBOT_RESTART_STARTED_AT", raising=False)
+
+    set_restart_notice_to_env(
+        channel="slack",
+        chat_id="C123",
+        metadata={"slack": {"thread_ts": "1700.42", "channel_type": "channel"}},
+    )
+
+    notice = consume_restart_notice_from_env()
+    assert notice is not None
+    assert notice.metadata == {
+        "slack": {"thread_ts": "1700.42", "channel_type": "channel"}
+    }
+    assert "NANOBOT_RESTART_NOTIFY_METADATA" not in os.environ
+
+
+def test_restart_notice_clears_stale_metadata(monkeypatch):
+    monkeypatch.setenv("NANOBOT_RESTART_NOTIFY_METADATA", '{"stale": true}')
+    set_restart_notice_to_env(channel="cli", chat_id="direct")
+    assert "NANOBOT_RESTART_NOTIFY_METADATA" not in os.environ
+
+
 def test_format_restart_completed_message_with_elapsed(monkeypatch):
     monkeypatch.setattr("nanobot.utils.restart.time.time", lambda: 102.0)
     assert format_restart_completed_message("100.0") == "Restart completed in 2.0s."