fix(voice): edits from the #705 review

- docs/api-reference.md and the voice-stream.ts overview now say a
  transcript frame is the current utterance so far and a final frame
  ends it, as the relay's own comment and the invariants doc do.
- VoiceInput.cleanup() hides the Send button before stop(true), so the
  button stays up for the words stop(true) salvaged and inserted.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/api-reference.md

@@ -1842,7 +1842,8 @@ same speech-to-text service the CLI's own `/voice` mode uses. Gated on the synce
   little-endian PCM, 16 kHz mono (<= 64 KB per frame), plus JSON control frames
   `{"t":"finalize"}` (ask for the final transcript) and `{"t":"stop"}`. Server
   sends `{"t":"ready"}`, `{"t":"transcript","text","final"}` (each frame is the
-  WHOLE running transcript, not a delta), `{"t":"error","message"}` and
+  current utterance so far, not a delta, and a `final: true` frame ends that
+  utterance), `{"t":"error","message"}` and
   `{"t":"closed"}`. Close codes: `4003` disallowed Host/Origin, `4004`
   unavailable (reason in the close reason), `4008` too many concurrent streams.
   Streams are capped in count and length (`src/config/voice.ts`).

src/web/public/voice-input.js

@@ -1415,11 +1415,13 @@ const VoiceInput = {
 
   /** Cleanup on SSE reconnect or page unload */
   cleanup() {
+    // Hide the Send button first: stop(true) below may insert the words it
+    // salvaged and show the button again for them.
+    this._hideVoiceSendBtn();
     if (this.isRecording) {
       this.stop(true);
       try { this.recognition?.abort(); } catch (_e) { /* already ended */ }
     }
-    this._hideVoiceSendBtn();
     DeepgramProvider._cleanup();
     ClaudeVoiceProvider._cleanup();
     this.recognition = null;

src/web/voice-stream.ts

@@ -13,9 +13,10 @@
  * - `{"type":"KeepAlive"}` on open and every 8s, or upstream drops the socket
  *   between utterances.
  * - Audio frames go up as raw binary.
- * - Downstream, `TranscriptText`/`TranscriptInterim` carry the RUNNING transcript
- *   (each frame supersedes the previous one — they are not deltas to concatenate),
- *   and `TranscriptEndpoint` promotes the pending interim to final.
+ * - Downstream, `TranscriptText`/`TranscriptInterim` carry the current utterance
+ *   so far (each frame supersedes the previous one; they are not deltas to
+ *   concatenate), and `TranscriptEndpoint` promotes the pending interim to final,
+ *   which ends that utterance.
  * - `{"type":"CloseStream"}` finalizes; the endpoint frame that follows is the
  *   last transcript, so `finalize()` waits briefly for it rather than closing.
  *