fix(app): prevent tab pruning from closing pinned archived agents

The tab sync effect pruned archived agent tabs without checking if they
were pinned, so clicking an archived agent from the sessions page would
open and immediately close the tab.

packages/app/src/screens/workspace/workspace-screen.tsx

@@ -983,6 +983,7 @@ function WorkspaceScreenContent({ serverId, workspaceId }: WorkspaceScreenProps)
       if (
         canPruneAgentTabs &&
         tab.target.kind === "agent" &&
+        !pinnedAgentIds.has(tab.target.agentId) &&
         shouldPruneWorkspaceAgentTab({
           agentId: tab.target.agentId,
           agentsHydrated: hasHydratedAgents,