Preserve loader behavior while reducing hidden work (#1996)

* fix(app): preserve loader behavior in retained panels

Keep the running footer mounted across panel switches. Inactive loaders stop their animation work, then realign to the original wall-clock phase before they become visible.

* perf(app): remove inactive loader wrapper worklet

* perf(app): pause hidden turn elapsed timers

* perf(app): reduce loader animation work

Keep one wall-clock-aligned clock for visible loaders and detach retained
hidden loaders without unmounting them. Preserve the 950 ms sequence and
reduced-motion behavior.

packages/app/src/agent-stream/view.tsx

@@ -772,7 +772,6 @@ const AgentStreamViewComponent = forwardRef<AgentStreamViewHandle, AgentStreamVi
         showRunningTurnFooter || bottomTurnFooterHost ? (
           <TurnFooter
             isRunning={showRunningTurnFooter}
-            isActive={isActive}
             inFlightTurnStartedAt={baseRenderModel.turnTiming.runningStartedAt}
             host={bottomTurnFooterHost}
             strategy={streamRenderStrategy}
@@ -781,7 +780,6 @@ const AgentStreamViewComponent = forwardRef<AgentStreamViewHandle, AgentStreamVi
         ) : null,
       [
         handleForkAssistantTurn,
-        isActive,
         showRunningTurnFooter,
         baseRenderModel.turnTiming.runningStartedAt,
         bottomTurnFooterHost,