Keep the replay progress helper private

Why: The frontend unused-export gate rejected a helper used only within its module.

Evidence: The unchanged knip baseline and TypeScript checks pass.

Impact: Remove an unnecessary export without changing replay behavior.

Refs: feature/workbench-flow-completion

src/live.ts

@@ -153,7 +153,7 @@ export function applyCheck(items: LiveItem[], passed: boolean, reason: string):
 
 /** A child streams cumulative previews. Replace that child's latest preview in
  * place, while preserving real phase changes and the order of other children. */
-export function applyAgentProgress(items: LiveItem[], agentRun: string, note: string): LiveItem[] {
+function applyAgentProgress(items: LiveItem[], agentRun: string, note: string): LiveItem[] {
   const text = note.trim()
   if (!text) return items
   for (let i = items.length - 1; i >= 0; i--) {