* WIP: fix archive tab reconciliation
* fix: converge archive into AgentManager for cross-session propagation
CLI archive left agent tabs visible in passive app clients because
Session.archiveAgentState only notified the archiving session's own
subscription. LoopService had the same gap via AgentManager.archiveAgent.
Converge on AgentManager.archiveAgent as the single canonical archive
path: persist updatedAt, call notifyAgentState before closeAgent so all
sessions receive the archived snapshot. Delete Session.archiveAgentState
and make handleArchiveAgentRequest a thin wrapper.
