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/components/agent-list.tsx

@@ -394,6 +394,7 @@ export function AgentList({
         serverId,
         agentId,
         workspaceId: agent.workspaceId,
+        pin: true,
       });
     },
     [isActionSheetVisible, onAgentSelect],

packages/app/src/components/archived-agent-callout.tsx

@@ -9,6 +9,7 @@ import { useHostRuntimeClient, useHostRuntimeIsConnected } from "@/runtime/host-
 import { useKeyboardShiftStyle } from "@/hooks/use-keyboard-shift-style";
 import { Button } from "@/components/ui/button";
 import type { Theme } from "@/styles/theme";
+import { toErrorMessage } from "@/utils/error-messages";
 
 interface ArchivedAgentCalloutProps {
   serverId: string;
@@ -21,6 +22,7 @@ export function ArchivedAgentCallout({ serverId, agentId }: ArchivedAgentCallout
   const client = useHostRuntimeClient(serverId);
   const isConnected = useHostRuntimeIsConnected(serverId);
   const [isUnarchiving, setIsUnarchiving] = useState(false);
+  const [unarchiveError, setUnarchiveError] = useState<string | null>(null);
 
   const { style: keyboardAnimatedStyle } = useKeyboardShiftStyle({ mode: "translate" });
 
@@ -32,10 +34,11 @@ export function ArchivedAgentCallout({ serverId, agentId }: ArchivedAgentCallout
   const handleUnarchive = useCallback(async () => {
     if (!client || !isConnected || isUnarchiving) return;
     setIsUnarchiving(true);
+    setUnarchiveError(null);
     try {
       await client.refreshAgent(agentId);
     } catch (error) {
-      console.error("[ArchivedAgentCallout] Failed to unarchive agent:", error);
+      setUnarchiveError(toErrorMessage(error));
       setIsUnarchiving(false);
     }
   }, [client, isConnected, isUnarchiving, agentId]);
@@ -44,16 +47,23 @@ export function ArchivedAgentCallout({ serverId, agentId }: ArchivedAgentCallout
     <Animated.View style={containerStyle}>
       <View style={styles.inputAreaContainer}>
         <View style={styles.inputAreaContent}>
-          <View style={styles.callout}>
-            <Text style={styles.calloutText}>{t("agentPanel.archived.callout")}</Text>
-            <Button
-              size="sm"
-              variant="secondary"
-              onPress={handleUnarchive}
-              disabled={!isConnected || isUnarchiving}
-            >
-              {t("agentPanel.archived.unarchive")}
-            </Button>
+          <View style={styles.calloutStack}>
+            <View style={styles.callout}>
+              <Text style={styles.calloutText}>{t("agentPanel.archived.callout")}</Text>
+              <Button
+                size="sm"
+                variant="secondary"
+                onPress={handleUnarchive}
+                disabled={!isConnected || isUnarchiving}
+              >
+                {t("agentPanel.archived.unarchive")}
+              </Button>
+            </View>
+            {unarchiveError ? (
+              <Text style={styles.errorText} testID="agent-unarchive-error">
+                {unarchiveError}
+              </Text>
+            ) : null}
           </View>
         </View>
       </View>
@@ -97,8 +107,16 @@ const styles = StyleSheet.create((theme: Theme) => ({
       md: theme.spacing[6],
     },
   },
+  calloutStack: {
+    gap: theme.spacing[2],
+  },
   calloutText: {
     color: theme.colors.foregroundMuted,
     fontSize: theme.fontSize.base,
   },
+  errorText: {
+    color: theme.colors.statusDanger,
+    fontSize: theme.fontSize.sm,
+    textAlign: "center",
+  },
 })) as unknown as Record<string, object>;