feat(webui): add lightweight session messaging via mentions

tests/agent/test_loop_progress.py

@@ -23,6 +23,7 @@ from nanobot.bus.outbound_events import (
 from nanobot.bus.queue import MessageBus
 from nanobot.providers.base import LLMResponse, ToolCallRequest
 from nanobot.providers.factory import ProviderSnapshot
+from nanobot.runtime_context import RUNTIME_CONTEXT_MESSAGE_META, detach_runtime_context
 from nanobot.session.webui_turns import WebuiTurnCoordinator, WebuiTurnRoutePolicy
 from nanobot.utils.progress_events import (
     invoke_file_edit_progress,
@@ -853,11 +854,16 @@ class TestToolEventProgress:
         assert len(requests) == 2
         assert requests[0][-1]["role"] == "user"
         assert requests[0][-1]["content"].endswith("Background research completed")
-        assert any(
-            message.get("role") == "user"
-            and message.get("content") == "Can you include the key detail?"
+        follow_up = next(
+            message
             for message in requests[1]
+            if message.get("role") == "user"
+            and str(message.get("content", "")).startswith("Can you include the key detail?")
         )
+        marker = follow_up["_meta"][RUNTIME_CONTEXT_MESSAGE_META]
+        detached = detach_runtime_context(follow_up["content"], marker)
+        assert detached is not None
+        assert detached[0] == "Can you include the key detail?"
         assert len(request_contexts) == 1
         request_ctx = request_contexts[0]
         assert request_ctx is not None