[eric] tree: group agent_manager helpers under agents/manager session and prompt

backend/apps/agents/manager/session/cloud_sync.py

@@ -0,0 +1,36 @@
+from datetime import datetime
+
+from backend.apps.agents.core.models import AgentSession
+from backend.apps.service.client import sync as _sync
+
+
+def _sync_session_close(session: AgentSession, close_reason: str = "user"):
+    """Submit the session state to the cloud on close. The cloud
+    consumes the dump however it sees fit; the desktop just hands off
+    a snapshot. Skipped for mock sessions so dev runs don't post to
+    the real backend.
+
+    Synthesizes a `closed_at` timestamp on the dump if the session
+    doesn't have one. Two paths previously sent close-events without
+    a timestamp and made the cloud unable to compute duration_ms
+    (which surfaced as duration_ms=null on 90% of session.ended events,
+    browser-agent and shutdown paths in particular):
+
+      1. browser_agent.py calls this without setting closed_at.
+      2. shutdown_all_sessions() clears closed_at to None for the
+         on-disk restore mechanism, then syncs.
+
+    Fix is here at the bottleneck rather than at every caller so we
+    can't miss a future call site. The on-disk session JSON keeps its
+    original (possibly None) closed_at, only the cloud-bound dump
+    gets the synthesized timestamp.
+    """
+    if close_reason == "mock" or getattr(session, "_mock_run", False):
+        return
+    try:
+        dump = session.model_dump(mode="json")
+        if not dump.get("closed_at"):
+            dump["closed_at"] = datetime.now().isoformat()
+        _sync(dump)
+    except Exception:
+        pass