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>

src/voice/voice_commands.py

@@ -0,0 +1,118 @@
+"""Detect in-band voice commands from STT transcripts.
+
+The voice pipeline transcribes Marius's speech via Whisper and dispatches the
+text to Claude. Some utterances are not questions for Claude — they're
+control commands for the voice stack itself. This module parses those out
+*before* the Claude round-trip so they take effect instantly and don't waste
+a Claude session turn.
+
+Currently handled:
+  * change TTS voice — "schimbă vocea pe M5", "vorbește cu vocea F3",
+    "voce em cinci", "voce feminină 3", etc.
+
+The parser is intentionally conservative: it requires BOTH a voice trigger
+word ("voce", "vorbește", "schimbă", "treci pe") AND a recognizable voice
+ID. A bare "M5" without context is NOT a command — Marius might be quoting
+a string.
+"""
+from __future__ import annotations
+
+import re
+from typing import Optional
+
+
+_VALID_VOICES = {f"M{i}" for i in range(1, 6)} | {f"F{i}" for i in range(1, 6)}
+
+
+# Trigger words that suggest the user is talking ABOUT the voice, not just
+# saying something that happens to contain a voice-ID-looking substring.
+_VOICE_TRIGGER_RE = re.compile(
+    r'\b(voce|vocea|voci|voice|vorbe[șs]te|schimb[aăÎ]|treci\s+pe)\b',
+    re.IGNORECASE,
+)
+
+# Direct form: "M5", "F 3", "m5", etc.
+_VOICE_ID_DIRECT_RE = re.compile(
+    r'\b([MF])\s*([1-5])\b',
+    re.IGNORECASE,
+)
+
+# Word form: "em cinci", "M trei", "masculin doi", "feminină patru", etc.
+# Whisper often transcribes "M5" as "em cinci" / "M cinci" because letter
+# names are spelled out phonetically in Romanian.
+_VOICE_ID_WORDS_RE = re.compile(
+    r'\b(em|m|masculin[aăe]?|ef|f|feminin[aăe]?)\s+(unu|una|doi|dou[ăa]|trei|patru|cinci|[1-5])\b',
+    re.IGNORECASE,
+)
+
+
+_DIGIT_WORD_TO_INT = {
+    'unu': 1, 'una': 1, 'unul': 1, '1': 1,
+    'doi': 2, 'două': 2, 'doua': 2, '2': 2,
+    'trei': 3, '3': 3,
+    'patru': 4, '4': 4,
+    'cinci': 5, '5': 5,
+}
+
+# Substring fallback: matches digit roots even when Whisper glues them into
+# compound non-words like "Mâcinci" (for "M cinci"=M5).
+_DIGIT_SUBSTR_RE = re.compile(
+    r'(cinci|patru|trei|dou[ăa]|unul|unu|una)',
+    re.IGNORECASE,
+)
+
+_F_GENDER_HINT_RE = re.compile(r'feminin|\bef\b|\bF\d?\b', re.IGNORECASE)
+
+
+def _normalize_gender(word: str) -> Optional[str]:
+    """Map gender word to 'M' or 'F'."""
+    w = word.lower()
+    if w in ('m', 'em') or w.startswith('masculin'):
+        return 'M'
+    if w in ('f', 'ef') or w.startswith('feminin'):
+        return 'F'
+    return None
+
+
+def detect_voice_change(text: str) -> Optional[str]:
+    """Parse a transcript for a 'change voice' command.
+
+    Returns the target voice id (one of M1-M5, F1-F5) or None if no command
+    was detected. Requires both a voice trigger word and a voice ID.
+    """
+    if not text:
+        return None
+    if not _VOICE_TRIGGER_RE.search(text):
+        return None
+    # Try the direct form first (M5, F3, etc.)
+    m = _VOICE_ID_DIRECT_RE.search(text)
+    if m:
+        candidate = f"{m.group(1).upper()}{m.group(2)}"
+        if candidate in _VALID_VOICES:
+            return candidate
+    # Fall back to the word form ("em cinci", "feminin trei", ...).
+    m = _VOICE_ID_WORDS_RE.search(text)
+    if m:
+        gender = _normalize_gender(m.group(1))
+        digit = _DIGIT_WORD_TO_INT.get(m.group(2).lower())
+        if gender is not None and digit is not None:
+            candidate = f"{gender}{digit}"
+            if candidate in _VALID_VOICES:
+                return candidate
+    # Permissive fallback: Whisper sometimes glues the letter into the next
+    # word ("Mâcinci" for "M cinci") or replaces it ("unul cinci" for
+    # "M unu cinci"). After a voice trigger word, scan for any digit-word
+    # substring and infer gender (F if a feminine marker is present, else M).
+    digit_hits = _DIGIT_SUBSTR_RE.findall(text)
+    digits = [_DIGIT_WORD_TO_INT[d.lower()] for d in digit_hits
+              if d.lower() in _DIGIT_WORD_TO_INT]
+    digits = [d for d in digits if 1 <= d <= 5]
+    if digits:
+        gender = 'F' if _F_GENDER_HINT_RE.search(text) else 'M'
+        # Last digit wins — handles "M unu cinci" → M5 since "unu" is a
+        # mangled letter-name prefix, "cinci" is the actual target.
+        return f"{gender}{digits[-1]}"
+    return None
+
+
+__all__ = ["detect_voice_change"]