feat(tui): make follow-up queue explicit

tui/src/prompt-queue.ts

@@ -5,10 +5,9 @@ export interface QueuedPrompt {
   options: MessageOptions
 }
 
-/** Owns the difference between steering the active turn and starting the next one. */
+/** Owns prompts that should start after the active turn finishes. */
 export class PromptQueue {
   private prompts: QueuedPrompt[] = []
-  private armed = false
 
   get length(): number {
     return this.prompts.length
@@ -16,30 +15,27 @@ export class PromptQueue {
 
   enqueue(prompt: QueuedPrompt): void {
     this.prompts.push(prompt)
-    this.armed = true
   }
 
-  /** A second Enter immediately promotes the newest queued prompt to steering. */
-  takeSteering(): QueuedPrompt | null {
-    if (!this.armed) return null
-    this.armed = false
+  takeLast(): QueuedPrompt | null {
     return this.prompts.pop() ?? null
   }
 
   takeFollowUp(): QueuedPrompt | null {
-    this.armed = false
     return this.prompts.shift() ?? null
   }
 
+  snapshot(): readonly QueuedPrompt[] {
+    return this.prompts
+  }
+
   restore(): QueuedPrompt[] {
     const prompts = this.prompts
     this.prompts = []
-    this.armed = false
     return prompts
   }
 
   clear(): void {
     this.prompts = []
-    this.armed = false
   }
 }