* 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.
Replace greedy agents Map subscription with a Zustand selector that
derives workspace agent visibility (ID sets only) with custom equality,
so the workspace screen only re-renders when agents are added, removed,
or archived — not on every status/activity update.
Fix tab pruning to check against all known agents (including archived)
instead of only active agents, so archived agent tabs survive
reconciliation. Remove the auto-unarchive effect that called
refreshAgent() as a workaround. Hide input area for archived agents.