Voice nodes (openpanel V4): stt, tts, wren reply/unhandled, socket publish

- `stt`: one realtime transcription session per utterance on the speech
  server's url, opened at `listening` true or the first chunk, committed at
  false; a whole clip goes to /v1/audio/transcriptions. Returns at once and
  publishes `partial` and `text` when the server answers.
- `tts`: one /v1/audio/speech call per sentence, cached by voice and text in
  node state; a reference is marked `append` while earlier ones still play.
- wren: `reply` says what was applied, `unhandled` carries the prompt when
  nothing was. The install hint names the git pin (PyPI's `wren` is another
  package).
- ai/client: transcribe, speak and transcribe_stream beside stream_completion.
- A device socket publishes scalar `in` ports as {"type": "publish"} text,
  in order with its binary frames.
- Pipeline.publish walks only what its values reach: a node downstream of a
  consumer that published nothing no longer runs again (wren re-acted on
  every microphone chunk).

docs/interface/dashboards.md

@@ -514,8 +514,10 @@ to 640×360. Re-encode other clips with the [clip recipe](../code/nodes.md#makin
 The device decides what its [port](#the-devices-own-ports) names
 mean. openpanel [reports](#what-a-device-reports) the ones it serves, such as
 `gpio.<n>`, `backlight`, `touch`, `mic` and `speaker`, with the settings each
-one reads, and ignores any other name. A browser screen serves none of them. The [speech recipe](../code/nodes.md#speech-to-and-from-a-panel)
-turns `mic` into text and text into `speaker`.
+one reads, and ignores any other name. A browser screen serves none of them. The
+[Speech to text](../reference/node-types.md#speech-to-text) and
+[Text to speech](../reference/node-types.md#text-to-speech) nodes turn `mic`
+into text and text into `speaker`, and `caption` shows what is being heard.
 
 ### The device's own ports