fix: keep Hermes session across runs and speak long replies as a digest (2.5.3)

Over the runs transport Hermes never reports the session it attached to a
run in the SSE stream, only in GET /v1/runs/{id}. EveFlow only read it in the
polling fallback, so the locally generated id was sent again and again and
each message opened a fresh Hermes session, losing the conversation context.
The client now adopts the run's session id after every run.

Long answers are now spoken as a digest: the first sentences (configurable,
4 by default) plus the closing question, followed by a short notice that the
full text is on screen. The default instructions ask Hermes to open long
replies with the essentials and to rely on the ongoing conversation.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ln4KL1feHtnV4nee4sZFhM

src/services/voice/tts.ts

@@ -115,12 +115,14 @@ export class TtsEngine {
     if (rest) for (const chunk of chunkForSpeech(rest)) this.enqueue(chunk);
   }
 
-  enqueue(text: string): void {
+  /** Queue one chunk; false when nothing speakable remains once markdown and code are stripped. */
+  enqueue(text: string): boolean {
     const item = this.makeItem(text);
-    if (!item) return;
+    if (!item) return false;
     this.queue.push(item);
     this.fillPrefetch();
     void this.drain();
+    return true;
   }
 
   private makeItem(text: string): QueueItem | null {