Restore archived agents from History (#2316)

* fix(app): restore archived agents from History

History navigation lost the explicit archived-agent intent during tab reconciliation, and workspace recovery stopped after restoring the workspace. Preserve the selected tab and recover its provider session as one action while serializing provider resume with timeline hydration.

* fix(app): preserve archived agent recovery invariants

* fix(server): preserve timeline hydration call shape

* fix(app): retain agent tabs through lookup

* fix(server): upgrade in-flight timeline broadcast

packages/app/src/stores/workspace-layout-actions.ts

@@ -194,6 +194,7 @@ interface ReorderPaneTabsInLayoutInput {
 export interface WorkspaceTabReconcileState {
   layout: WorkspaceLayout;
   pinnedAgentIds?: ReadonlySet<string> | null;
+  pendingAgentIds?: ReadonlySet<string> | null;
   hiddenAgentIds?: ReadonlySet<string> | null;
 }
 
@@ -1653,13 +1654,14 @@ interface EntityTabGroup {
 function applyPinnedAndHidden(input: {
   baseAgentIds: Set<string>;
   pinnedAgentIds: Set<string>;
+  pendingAgentIds: Set<string>;
   hiddenAgentIds: Set<string>;
   knownAgentIds: Set<string>;
 }): Set<string> {
-  const { baseAgentIds, pinnedAgentIds, hiddenAgentIds, knownAgentIds } = input;
+  const { baseAgentIds, pinnedAgentIds, pendingAgentIds, hiddenAgentIds, knownAgentIds } = input;
   const result = new Set(baseAgentIds);
   for (const agentId of pinnedAgentIds) {
-    if (knownAgentIds.has(agentId)) {
+    if (knownAgentIds.has(agentId) || pendingAgentIds.has(agentId)) {
       result.add(agentId);
     }
   }
@@ -1784,6 +1786,7 @@ export function reconcileWorkspaceTabs(
     findPaneById(nextLayout.root, nextLayout.focusedPaneId)?.focusedTabId ?? null;
   let reconciledFocusedTabId = originalFocusedTabId;
   const pinnedAgentIds = new Set(state.pinnedAgentIds ?? []);
+  const pendingAgentIds = new Set(state.pendingAgentIds ?? []);
   const hiddenAgentIds = new Set(state.hiddenAgentIds ?? []);
   const activeAgentIds = normalizeStringSet(snapshot.activeAgentIds);
   const autoOpenAgentIds = normalizeStringSet(snapshot.autoOpenAgentIds);
@@ -1795,12 +1798,14 @@ export function reconcileWorkspaceTabs(
   const visibleAgentIds = applyPinnedAndHidden({
     baseAgentIds: activeAgentIds,
     pinnedAgentIds,
+    pendingAgentIds,
     hiddenAgentIds,
     knownAgentIds,
   });
   const autoOpenSet = applyPinnedAndHidden({
     baseAgentIds: autoOpenAgentIds,
     pinnedAgentIds,
+    pendingAgentIds,
     hiddenAgentIds,
     knownAgentIds,
   });