perf(app): keep warm workspace switching responsive (#3447)

* perf(app): reduce warm workspace switch work

Retained workspaces avoided mounts but pane activity still rerendered the full composer, message input, and agent-control presentation. Keep the activity contract intact while moving focus-sensitive behavior behind small context consumers, and add a Playwright benchmark that measures rapid retained workspace switching on one browser clock.

* perf(app): accelerate retained workspace switching

Avoid repeated retained-stream layout reconciliation and unrelated workspace structure recomputation. Use the lightweight route transition while the host is already focused, while preserving targeted root POP_TO for returns from app-wide routes where it prevents duplicate hidden decks.

* perf(app): defer composer focus during workspace switches

* perf(app): retain recently used workspaces longer

Keep up to ten workspace screens warm so normal multi-workspace navigation does not repeatedly rebuild recently used timelines. Inactive screens expire after ten minutes, while the active screen remains protected and capacity eviction stays least-recently-used.

* fix(app): reconcile retained timeline geometry

* fix(app): refresh retained reading position

packages/app/src/composer/agent-controls/index.tsx

@@ -64,7 +64,11 @@ import { readMeasuredWidth } from "@/hooks/use-container-width";
 import { useToast } from "@/contexts/toast-context";
 import { toErrorMessage } from "@/utils/error-messages";
 import { showProviderNoticeToast } from "@/utils/provider-notice-toast";
-import { useAgentControlCommandCenterActions } from "@/command-center/agent-control-registration";
+import {
+  useAgentControlCommandCenterActions,
+  type AgentControlCommandCenterSource,
+} from "@/command-center/agent-control-registration";
+import { useComposerKeyboardScope } from "@/composer/keyboard-scope";
 import { isNative } from "@/constants/platform";
 import {
   resolveComposerControlDensity,
@@ -154,11 +158,28 @@ export interface DraftAgentControlsProps {
 interface AgentControlsProps {
   agentId: string;
   serverId: string;
-  isPaneFocused: boolean;
   onDropdownClose?: () => void;
   isCompactLayout?: boolean;
 }
 
+function AgentControlCommandCenterRegistration({
+  sourceId,
+  enabled,
+  controls,
+}: {
+  sourceId: string;
+  enabled: boolean;
+  controls: AgentControlCommandCenterSource;
+}) {
+  const { isActiveComposer } = useComposerKeyboardScope();
+  useAgentControlCommandCenterActions({
+    sourceId,
+    enabled: enabled && isActiveComposer,
+    controls,
+  });
+  return null;
+}
+
 function findOptionLabel(
   options: AgentControlOption[] | undefined,
   selectedId: string | undefined,
@@ -1477,7 +1498,6 @@ function ThinkingComboboxOption({
 export const AgentControls = memo(function AgentControls({
   agentId,
   serverId,
-  isPaneFocused,
   onDropdownClose,
   isCompactLayout,
 }: AgentControlsProps) {
@@ -1649,10 +1669,8 @@ export const AgentControls = memo(function AgentControls({
     [agentId, agentProvider, client, toast, updatePreferences],
   );
 
-  useAgentControlCommandCenterActions({
-    sourceId: `agent:${serverId}:${agentId}`,
-    enabled: isPaneFocused && Boolean(client),
-    controls: {
+  const commandCenterControls = useMemo<AgentControlCommandCenterSource>(
+    () => ({
       serverId,
       ownerKey: agentId,
       provider: agentProvider,
@@ -1673,8 +1691,31 @@ export const AgentControls = memo(function AgentControls({
         list: agent?.features,
         set: handleSetFeature,
       },
-    },
-  });
+    }),
+    [
+      activeModelId,
+      agent?.features,
+      agentId,
+      agentModelSelectorProviders,
+      agentProvider,
+      commandCenterModes,
+      handleSelectCommandCenterModel,
+      handleSelectThinkingOption,
+      handleSetFeature,
+      modeProviderDefinitions,
+      modelSelection.selectedThinkingId,
+      modelSelection.thinkingOptions,
+      serverId,
+    ],
+  );
+
+  const commandCenterRegistration = (
+    <AgentControlCommandCenterRegistration
+      sourceId={`agent:${serverId}:${agentId}`}
+      enabled={Boolean(client)}
+      controls={commandCenterControls}
+    />
+  );
 
   const handleModelSelectorOpen = useCallback(() => {
     refetchSnapshotIfStale(agentProvider);
@@ -1692,30 +1733,33 @@ export const AgentControls = memo(function AgentControls({
   }
 
   return (
-    <ControlledAgentControls
-      provider={agent.provider}
-      modelSelectorProviders={agentModelSelectorProviders}
-      modelOptions={modelOptions}
-      selectedModelId={modelSelection.activeModelId ?? undefined}
-      onSelectModel={handleSelectModel}
-      agentProfiles={agentProfiles}
-      onApplyAgentProfile={agentProfiles?.applyProfile}
-      onEditAgentProfiles={handleEditAgentProfiles}
-      thinkingOptions={thinkingOptions.length > 1 ? thinkingOptions : undefined}
-      selectedThinkingOptionId={modelSelection.selectedThinkingId ?? undefined}
-      onSelectThinkingOption={handleSelectThinkingOption}
-      features={agent.features}
-      onSetFeature={handleSetFeature}
-      isModelLoading={snapshotIsLoading || selectedProviderIsLoading}
-      onModelSelectorOpen={handleModelSelectorOpen}
-      onRetryModelProvider={handleRetryModelProvider}
-      isRetryingModelProvider={snapshotIsRefreshing}
-      onDropdownClose={onDropdownClose}
-      disabled={!client}
-      modeControl={modeControl}
-      modelSelectorServerId={serverId}
-      isCompactLayout={isCompactLayout}
-    />
+    <>
+      {commandCenterRegistration}
+      <ControlledAgentControls
+        provider={agent.provider}
+        modelSelectorProviders={agentModelSelectorProviders}
+        modelOptions={modelOptions}
+        selectedModelId={modelSelection.activeModelId ?? undefined}
+        onSelectModel={handleSelectModel}
+        agentProfiles={agentProfiles}
+        onApplyAgentProfile={agentProfiles?.applyProfile}
+        onEditAgentProfiles={handleEditAgentProfiles}
+        thinkingOptions={thinkingOptions.length > 1 ? thinkingOptions : undefined}
+        selectedThinkingOptionId={modelSelection.selectedThinkingId ?? undefined}
+        onSelectThinkingOption={handleSelectThinkingOption}
+        features={agent.features}
+        onSetFeature={handleSetFeature}
+        isModelLoading={snapshotIsLoading || selectedProviderIsLoading}
+        onModelSelectorOpen={handleModelSelectorOpen}
+        onRetryModelProvider={handleRetryModelProvider}
+        isRetryingModelProvider={snapshotIsRefreshing}
+        onDropdownClose={onDropdownClose}
+        disabled={!client}
+        modeControl={modeControl}
+        modelSelectorServerId={serverId}
+        isCompactLayout={isCompactLayout}
+      />
+    </>
   );
 });