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/hooks/use-agent-screen-state-machine.test.ts

@@ -57,6 +57,7 @@ function createAgentWithStatus({ id, status }: { id: string; status: Agent["stat
 function createBaseInput(): AgentScreenMachineInput {
   return {
     agent: null,
+    isArchived: false,
     continuity: { kind: "none" },
     missingAgentState: { kind: "idle" },
     isConnected: true,
@@ -385,6 +386,22 @@ describe("deriveAgentScreenViewState", () => {
     expect(result.memory.lastReadyAgent).toBeNull();
   });
 
+  it("renders an archived agent before provider history is initialized", () => {
+    const result = deriveAgentScreenViewState({
+      input: {
+        ...createBaseInput(),
+        agent: createAgent("agent-1"),
+        isArchived: true,
+        needsAuthoritativeSync: true,
+      },
+      memory: createBaseMemory(),
+    });
+
+    const ready = expectReadyState(result.state);
+    expect(ready.agent.id).toBe("agent-1");
+    expect(ready.sync).toEqual({ status: "idle" });
+  });
+
   it("keeps optimistic create non-blocking while timeline and authoritative history catch up", () => {
     const memory = createBaseMemory();
     const input: AgentScreenMachineInput = {

packages/app/src/hooks/use-agent-screen-state-machine.ts

@@ -41,6 +41,7 @@ export type AgentScreenMissingState =
 
 export interface AgentScreenMachineInput {
   agent: AgentScreenAgent | null;
+  isArchived: boolean;
   missingAgentState: AgentScreenMissingState;
   isConnected: boolean;
   isArchivingCurrentAgent: boolean;
@@ -61,6 +62,7 @@ function hasOptimisticCreateContinuity(input: AgentScreenMachineInput): boolean
 
 function shouldBlockInitialAuthoritativeReadyState(input: AgentScreenMachineInput): boolean {
   return (
+    !input.isArchived &&
     !hasOptimisticCreateContinuity(input) &&
     !input.hasHydratedHistoryBefore &&
     (input.needsAuthoritativeSync || input.isHistorySyncing)
@@ -164,6 +166,9 @@ function resolveAgentScreenSync(args: {
   hadInitialSyncFailure: boolean;
 }): AgentScreenReadySyncState {
   const { input, hadInitialSyncFailure } = args;
+  if (input.isArchived) {
+    return { status: "idle" };
+  }
   if (!input.isConnected) {
     return { status: "reconnecting" };
   }