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.
Mohamed Boudra