Three follow-up atomics on top of the contacts/topics/sync wave.
## 1. AskLanguage state + ru/en localisation (default en)
New state `AskLanguage` inserted between `Intro` and `AskName`. Intro now
sends a bilingual greeting + language picker. AskLanguage parses
en/english/1/ru/русский/2/etc → persona_patch{"language":"<code>"} →
transitions to AskName with that language's prompt.
All later prompts (AskName / AskTone / AskInterests / AskHobbies /
TopicSpecifics / TopicNowLater / TopicResearch / AskSchedule / Ready)
read persona.language via Lang::from_persona and dispatch through
Strings::* helpers — two language tables, no fallthrough.
Back-compat migration: existing chats without `language` key (like the
user currently in topic_now_later) get an implicit "ru" patch on next
turn so their Russian onboarding continues without regression.
New files: strings.rs (164), machine_lang.rs (145).
Modified: state.rs (+AskLanguage variant), machine.rs (Intro→AskLanguage,
AskLanguage arm, migration guard), machine_helpers.rs, machine_tests.rs.
5 new tests (intro_to_ask_language, ask_language_en, ask_language_ru,
ask_language_invalid, migration_sets_ru_when_language_missing).
## 2. Real proposeTopicSources — removed TODO(phase2) stub
machine_lang.rs::step_topic_research now calls
extractor.extract(prompt, topic_title) with a {name, url, why} schema.
Parses JSON, formats numbered source list, transitions to TopicSources.
Failure paths (LLM error, empty array): graceful fallback prompt asking
user to suggest their own — still transitions to TopicSources so flow
doesn't deadlock.
3 new tests in machine_tests_topic_research.rs:
topic_research_yes_proposes_sources,
topic_research_yes_empty_sources_still_advances,
topic_research_no_skips_topic_sources.
## 3. Voice-message handling (Telegram voice/audio → STT → text pipeline)
kei-telegram-webhook: added Voice/Audio sub-structs on Message and
WebhookEvent::Voice variant. classify() detects message.voice OR
message.audio. 2 new tests in event.rs.
kei-buddy/src/voice.rs (178 LOC):
VoiceHandler { bot_token, stt: Arc<dyn SttBackend>, http }
transcribe_file(file_id, mime_type) does:
1. GET https://api.telegram.org/bot{token}/getFile?file_id=...
2. GET https://api.telegram.org/file/bot{token}/{file_path}
3. SttRequest { audio_bytes, mime_type, language: None } → backend.transcribe
4. Returns transcript text.
2 wiremock tests (download chain + 500 error mapping).
serve.rs adds voice: Option<Arc<VoiceHandler>> to BuddyContext;
on_event Voice arm: whitelist check → transcribe → handle_text (same
pipeline as if user typed). Voice unavailable: warn + ignore.
serve_runner.rs builds VoiceHandler from KEI_BUDDY_STT_BACKEND env.
kei-stt added as optional dep gated by serve feature. Default backend
whisper-local (no extra build deps).
TTS reply path deferred (next atomic).
## Verify
* cargo check --workspace: PASS
* cargo test -p kei-buddy --lib: 55 passed / 0 failed (was 41 → 50 → 53 → 55)
* cargo test -p kei-telegram-webhook --lib: 7 passed (was 5, +2 voice)
* cargo build -p kei-buddy --release: PASS (23.7s)
NOT deployed yet — three new things to roll out next:
* новые миграции (нет — БД без изменений)
* новые env: KEI_BUDDY_STT_BACKEND (optional)
* установка faster-whisper / piper-tts на сервер для STT
(без него Voice event просто warn-логируется и игнорируется)
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