Adds text-to-speech output to the Telegram channel, mirroring the
existing WhatsApp Web voice-chat implementation. When a user sends a
voice note (transcribed via STT), the channel enters voice-chat mode
and subsequent agent replies are synthesised into a Telegram voice note
via the configured TTS provider, in addition to the normal text reply.
Sending a text message exits voice-chat mode.
Implementation details:
- Add `tts_config`, `voice_chats`, and `pending_voice` fields to
`TelegramChannel`
- Add `with_tts()` builder method, gated on `config.enabled`
- Track voice-chat state: enter on successful STT transcription, exit
on incoming text message
- `synthesize_and_send_voice()` static method: synthesises audio via
`TtsManager` and uploads to Telegram using `sendVoice` multipart API
- 10-second debounce in `send()` ensures only the final substantive
reply in a tool chain gets a voice note (skips JSON, code blocks,
URLs, short status messages)
- Wire `.with_tts(config.tts.clone())` into both Telegram construction
sites in the channel factory
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
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