fix(tts): add speak() for complete responses; fix briefing message commit race

frontend/src/composables/useStreamingTts.ts

@@ -52,6 +52,8 @@ export interface UseStreamingTtsReturn {
   speaking: ComputedRef<boolean>
   /** Cancel all in-flight synthesis/playback and clear the queue. */
   stop: () => void
+  /** Speak a complete text through the same sentence-chunking pipeline. */
+  speak: (text: string) => void
 }
 
 export function useStreamingTts(options: UseStreamingTtsOptions): UseStreamingTtsReturn {
@@ -139,5 +141,18 @@ export function useStreamingTts(options: UseStreamingTtsOptions): UseStreamingTt
     }
   })
 
-  return { speaking, stop }
+  function speak(text: string): void {
+    stop()
+    if (!text.trim()) return
+    const myAbortId = abortId
+    const { sentences, remainder } = extractSentences(text)
+    for (const sentence of sentences) {
+      enqueueSentence(sentence, myAbortId)
+    }
+    if (remainder.trim().length >= MIN_CHARS) {
+      enqueueSentence(remainder.trim(), myAbortId)
+    }
+  }
+
+  return { speaking, stop, speak }
 }