The status-bar "Agents" item conflated three unrelated signals — running
subagents (aggregated across all sessions), in-flight session turns, and
failed background *system* actions (gateway restarts, toolset installs,
computer-use grants via $desktopActionTasks/preview restart) — yet
clicking it opens AgentsView, which renders only subagents. A failed
gateway restart therefore showed "Agents (1 Failed)" over an empty
"No live subagents" tree. AgentsView also filtered to the active session,
so a subagent running in a background session showed "Agents N running"
with nothing in the tree (the desync reported in #49808).
Unify the scope both surfaces speak:
- AgentsView aggregates subagents across every session (salvages #49819).
- The indicator's running/failed counts come from subagents only
(aggregated), never background system actions — those keep their own
surfaces in settings / command center.
So "Agents (N …)" now always points at a populated Spawn tree.
Supersedes #49819. Fixes#49808.
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