WIP: fix archive tab reconciliation (#158)

* 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.

packages/app/src/screens/workspace/workspace-agent-visibility.test.ts

@@ -102,6 +102,17 @@ describe("workspace agent visibility", () => {
     ).toBe(true);
   });
 
+  it("prunes pinned archived agent tabs because archive state is authoritative", () => {
+    expect(
+      shouldPruneWorkspaceAgentTab({
+        agentId: "archived-agent",
+        agentsHydrated: true,
+        knownAgentIds: new Set(["archived-agent"]),
+        activeAgentIds: new Set<string>(),
+      }),
+    ).toBe(true);
+  });
+
   it("does not prune active agent tabs", () => {
     const knownAgentIds = new Set(["active-agent"]);
     const activeAgentIds = new Set(["active-agent"]);

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

@@ -952,7 +952,6 @@ function WorkspaceScreenContent({ serverId, workspaceId }: WorkspaceScreenProps)
       if (
         canPruneAgentTabs &&
         tab.target.kind === "agent" &&
-        !pinnedAgentIds.has(tab.target.agentId) &&
         shouldPruneWorkspaceAgentTab({
           agentId: tab.target.agentId,
           agentsHydrated: hasHydratedAgents,