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/adapters/discord_voice.py

@@ -21,6 +21,14 @@ from typing import Optional
 import discord
 from discord import app_commands
 
+# Optional DAVE dep (mandatory at runtime when discord.py 2.7.1 is paired with
+# Discord voice gateway v=8; tolerated missing in tests / dev environments).
+try:
+    import davey
+    _HAS_DAVE = True
+except ImportError:
+    _HAS_DAVE = False
+
 from src.config import Config
 from src.voice.pipeline import (
     VoiceSession,
@@ -28,7 +36,7 @@ from src.voice.pipeline import (
     _get_whisper_model,
     _get_silero_vad,
 )
-from src.voice.tts_stream import TTSQueue
+from src.voice.tts_stream import TTSQueue, EchoStreamingAudioSource
 from src.voice._discord_voice_adapter import connect_voice
 
 log = logging.getLogger("echo-core.discord.voice")
@@ -53,6 +61,11 @@ async def warmup_models() -> None:
     """
     global _voice_load_error
     try:
+        if not discord.opus.is_loaded():
+            discord.opus.load_opus("libopus.so.0")
+        if _HAS_DAVE:
+            log.info("DAVE protocol v%d available (davey %s)",
+                     davey.DAVE_PROTOCOL_VERSION, davey.__version__)
         await asyncio.to_thread(_get_whisper_model)
         await asyncio.to_thread(_get_silero_vad)
         log.info("Voice models warm")
@@ -167,11 +180,24 @@ def register(tree: app_commands.CommandTree, bot: discord.Client) -> app_command
             )
             return
         _voice_sessions[guild_id] = session
-        # Wake-up beep
+        # Start TTS streaming source for the entire session. Chain the
+        # wake-up beep via `after=` so streaming takes over when beep ends.
+        def _start_stream(error: Optional[Exception] = None) -> None:
+            if error is not None:
+                log.warning("Beep playback ended with error: %s", error)
+            try:
+                vc.play(EchoStreamingAudioSource(ttsq))
+                log.info("TTS streaming source attached")
+            except Exception:
+                log.exception("EchoStreamingAudioSource attach failed")
         try:
-            vc.play(discord.FFmpegPCMAudio("assets/voice/beep_200ms.wav"))
+            vc.play(
+                discord.FFmpegPCMAudio("assets/voice/beep_200ms.wav"),
+                after=_start_stream,
+            )
         except Exception:
-            log.warning("Beep playback skipped", exc_info=True)
+            log.warning("Beep playback skipped, starting stream directly", exc_info=True)
+            _start_stream()
         # Attach sink
         try:
             bot_user_id = int(bot.user.id) if bot.user is not None else 0
@@ -220,6 +246,45 @@ def register(tree: app_commands.CommandTree, bot: discord.Client) -> app_command
             log.warning("Presence reset skipped", exc_info=True)
         await interaction.followup.send("Plecat.", ephemeral=True)
 
+    _VOICE_CHOICES = [
+        app_commands.Choice(name=v, value=v)
+        for v in ("M1", "M2", "M3", "M4", "M5", "F1", "F2", "F3", "F4", "F5")
+    ]
+
+    @voice_group.command(name="setvoice", description="Schimbă vocea Echo (M1-M5 sau F1-F5)")
+    @app_commands.describe(voice="Voce nouă")
+    @app_commands.choices(voice=_VOICE_CHOICES)
+    async def setvoice(
+        interaction: discord.Interaction,
+        voice: app_commands.Choice[str],
+    ) -> None:
+        await interaction.response.defer(ephemeral=True)
+        new_voice = voice.value
+        # Live-swap on the active session if Echo is in voice on this guild.
+        guild_id = interaction.guild.id if interaction.guild else None
+        session = _voice_sessions.get(guild_id) if guild_id is not None else None
+        live_swapped = False
+        if session is not None and session.ttsq is not None:
+            session.ttsq.voice_id = new_voice
+            live_swapped = True
+        # Persist as the new default for future sessions.
+        try:
+            cfg = Config()
+            cfg.set("voice.default_voice", new_voice)
+            cfg.save()
+        except Exception as e:
+            log.warning("config save failed for new default voice: %s", e)
+            await interaction.followup.send(
+                f"Voce schimbată live ({new_voice}), dar config-ul nu s-a salvat: {e}",
+                ephemeral=True,
+            )
+            return
+        if live_swapped:
+            msg = f"Vocea schimbată **live** pe {new_voice}. Următoarea frază va folosi vocea nouă."
+        else:
+            msg = f"Default voce setată {new_voice}. Va intra în vigoare la următorul /voice join."
+        await interaction.followup.send(msg, ephemeral=True)
+
     @voice_group.command(name="doctor", description="Verifică voice stack")
     async def doctor(interaction: discord.Interaction) -> None:
         await interaction.response.defer(ephemeral=True)