feat(voice): DAVE E2E + full voice UX (squash of voice/dave-recv)

Squashed branch: voice/dave-recv → master. Closes Pas 12 (DAVE E2E) and lands
voice-mode UX polish + verbal voice control on top of the Pas 1-10 scaffolding
already on master.

## DAVE E2E receive-side decrypt (e4f3177)

Vendored fork: discord-ext-voice-recv 0.5.3a+echo.dave1. Patches the receive
pipeline to handle Discord's mandatory DAVE encryption on voice gateway v=8.
- `_maybe_dave_decrypt`: uses davey.can_passthrough(user_id) as primary gate,
  falls through to dave.decrypt for DAVE-epoch peers, drops on decrypt failure
  without killing the reader thread.
- VAD fix: silero-vad v5+ requires exactly 512 samples; our 100ms window
  (1600 samples) was silently raising ValueError → STT never fired. Now slice
  into 512-sample chunks.
- Whisper: bumped beam_size 1→5 and added RO initial_prompt.
- Tests: 11 DAVE unit tests + 2 callback integration tests + contract test
  with fork-version guard.

## Voice UX polish (d1bc77e)

- Killed the 3s "mă gândesc" filler (always collided with Claude p50 4-7s).
- Barge-in via `ttsq.clear()` at top of `on_segment_done`.
- DTX silence-flush poller (200ms tick) — Discord stops sending RTP packets
  when silent, so the inline silence-check in sink.write() never fired for
  trailing audio; background thread handles it.
- `EchoStreamingAudioSource.read()` non-blocking — old `get_frame(timeout=0.1)`
  wrecked Discord's 20ms cadence and the client interpreted bursts as
  stuttering (Marius heard "4 de minute" instead of full sentence).
- RO time expansion: 23:09 → "douăzeci și trei și nouă minute".
- Supertonic Unicode sanitize centralized in tools/tts.py.
- Whisper local_files_only=True — no HF metadata GET on each startup.
- Diagnostic logging through sink → VAD → Claude stream → TTS chain.

## Voice mode iteration (e589e48)

- `personality/VOICE_MODE.md` — voice-tailored system prompt (short, no
  markdown, no abbreviations, time without seconds, distances in
  "mii"/"milioane"); plumbed via build_system_prompt(voice_mode=True).
- Isolated voice session key `voice:<channel_id>` — voice doesn't share
  context with text adapter on the same channel; auto-applied without
  /clear ceremony. /clear drops both keys.
- Metric units + Romanian thousands (normalize.py): "384.000 km" →
  "trei sute optzeci și patru de mii de kilometri" with feminine-correct
  pluralization and "de" particle for ≥20.
- `/voice setvoice <M1-F5>` slash command with native autocomplete; swaps
  live + persists voice.default_voice to config.json.
- Verbal voice change (src/voice/voice_commands.py + 29 tests) — "schimbă
  vocea pe M5", "voce em cinci", with permissive substring fallback for
  Whisper-mangled forms like "Mâcinci"=M5 and "unul cinci"=M5. Whisper
  initial_prompt now lists voice vocabulary to bias STT toward clean
  outputs.
- Fast barge-in: VAD ≥2 consecutive windows (~200ms) on Marius's user
  while Echo has pending TTS frames → cut him off mid-sentence so user
  doesn't wait the full silence + STT cycle. Acoustic echo bleed-through
  still requires headphones (no AEC).

## Test suite

130 voice + router tests pass (test_voice_recv_dave, test_voice_session_cleanup,
test_voice_adapter_contract, test_voice_normalize, test_voice_commands,
test_router).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tasks/lessons.md

@@ -17,6 +17,13 @@ Lecții capturate din corectările lui Marius. Citește acest fișier la începu
 
 <!-- Lecțiile se adaugă mai jos, cele mai noi sus. -->
 
+## Supertonic rejectează ghilimelele curly (Unicode) cu HTTP 500
+**Data:** 2026-05-27
+**Context:** Marius a dat o comandă audio pe Discord cu un URL, iar răspunsul lui Claude conținea `„foo"` (ghilimele românești curly). Supertonic a returnat `HTTP 500: synthesis failed: Found 1 unsupported character(s): ['„']` și răspunsul nu s-a mai auzit. Fără retry logic vizibil în UX — pur și simplu tace.
+**Greșeala:** Am presupus că `normalize_for_tts` produce text deja "TTS-safe" pentru Supertonic. În realitate `strip_markdown` păstrează ghilimelele Unicode (`„` U+201E, `"` U+201D, `—` U+2014, `…` U+2026, etc.) pe care Supertonic le refuză.
+**Regula:** Înainte de orice apel HTTP la Supertonic, **sanitizează punctuația Unicode** la echivalentele ASCII (`„` `"` `"` → `"`, `'` `'` `‚` → `'`, `–` `—` → `-`, `…` → `...`, `«` `»` → `"`). Funcția `sanitize_punctuation` în `src/voice/normalize.py` face asta și e apelată chiar după `strip_markdown` în pipeline. Dacă apar caractere noi care crapă Supertonic (ex: simboluri matematice, săgeți), adaugă-le în `_TTS_PUNCT_MAP`.
+**Când se aplică:** Orice cod care trimite text la Supertonic (`tools/tts.py`, `src/voice/tts_stream.py`). Inclusiv testare manuală cu `curl` — folosește text românesc realistic (include `„foo"`, em-dash `—`, ellipsis `…`).
+
 ## Mai multe threads ≠ mai rapid — fitează `cpu_threads` pe physical cores, nu logical
 **Data:** 2026-05-27
 **Context:** Benchmark `tools/voice_bench.py` pentru faster-whisper `small` int8 pe i7-6700T (4 physical / 8 logical cores). Marius a urcat VM-ul de la 2 → 4 → 6 cores online, așteptând că mai multe = mai rapid.