feat: harden runtime readiness and session workflow

frontend/src/shell/CentralStatus.tsx

@@ -17,7 +17,7 @@ function tailLines(s: string, n = 5): string[] {
  *  (elapsed time + a short tail of the model stream) while the model is busy, and the
  *  gate's curated messages for the current step. The full verbose stream lives in the
  *  left Model-activity panel. */
-export function CentralStatus({ working }: { working: boolean }) {
+export function CentralStatus({ working, workingLabel }: { working: boolean; workingLabel?: string }) {
   const lastUserEntry = useSessionStore((s) => s.lastUserEntry);
   const stepMessages = useSessionStore((s) => s.stepMessages);
   const transcript = useSessionStore((s) => s.transcript);
@@ -62,7 +62,7 @@ export function CentralStatus({ working }: { working: boolean }) {
               <WorkingSpinner spinning className="size-3.5" />
             </span>
             <span className="shrink-0 font-mono tabular-nums">{elapsed}s</span>
-            <span className="sr-only">ThothII is working</span>
+            <span>{workingLabel ?? "ThothII is working"}</span>
           </div>
           {tailRows.length > 0 && (
             <ol className="ml-7 flex flex-col gap-0.5 overflow-hidden rounded-lg border border-border/60 bg-muted/40 px-3 py-2">