Inbox: people before system notices and newest first; wait wakes on new or human messages, not an old notice backlog; mark_read MCP tool

DeepSeek's inbox was buried under 78 automatic baseline notices read oldest
first, so it missed direct answers.

tests/test_core.py

@@ -209,7 +209,7 @@ class Review(HarborCase):
             self.h.transition("DeepSeek", item["id"], "approved")
         self.h.transition("Claude", item["id"], "in_review")
         self.h.transition("Claude", item["id"], "changes_requested", note="movsx: signed read")
-        self.assertEqual(self.h.inbox("DeepSeek")[-1]["kind"], "request")
+        self.assertEqual(self.h.inbox("DeepSeek")[0]["kind"], "request")
         self.h.transition("DeepSeek", item["id"], "submitted", commit="def5678")
         self.h.transition("Kimi", item["id"], "approved")
         with self.assertRaises(HarborError):