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>

tests/test_router.py

@@ -30,7 +30,10 @@ class TestClearCommand:
         response, is_cmd = route_message("ch-1", "user-1", "/clear")
         assert response == "Session cleared. Model reset to sonnet."
         assert is_cmd is True
-        mock_clear.assert_called_once_with("ch-1")
+        # /clear drops both the text-adapter session and the isolated voice
+        # session for the same Discord channel.
+        mock_clear.assert_any_call("ch-1")
+        mock_clear.assert_any_call("voice:ch-1")
 
     @patch("src.router._get_config")
     @patch("src.router.clear_session")
@@ -191,7 +194,7 @@ class TestRegularMessage:
         response, is_cmd = route_message("ch-1", "user-1", "hello")
         assert response == "Hello from Claude!"
         assert is_cmd is False
-        mock_send.assert_called_once_with("ch-1", "hello", model="sonnet", on_text=None)
+        mock_send.assert_called_once_with("ch-1", "hello", model="sonnet", on_text=None, voice_mode=False)
 
     @patch("src.router.send_message")
     def test_model_override(self, mock_send):
@@ -199,7 +202,7 @@ class TestRegularMessage:
         response, is_cmd = route_message("ch-1", "user-1", "hello", model="opus")
         assert response == "Response"
         assert is_cmd is False
-        mock_send.assert_called_once_with("ch-1", "hello", model="opus", on_text=None)
+        mock_send.assert_called_once_with("ch-1", "hello", model="opus", on_text=None, voice_mode=False)
 
     @patch("src.router._get_channel_config")
     @patch("src.router._get_config")
@@ -227,7 +230,7 @@ class TestRegularMessage:
 
         cb = lambda t: None
         route_message("ch-1", "user-1", "hello", on_text=cb)
-        mock_send.assert_called_once_with("ch-1", "hello", model="sonnet", on_text=cb)
+        mock_send.assert_called_once_with("ch-1", "hello", model="sonnet", on_text=cb, voice_mode=False)
 
 
 # --- _get_channel_config ---
@@ -269,7 +272,7 @@ class TestModelResolution:
         mock_chan_cfg.return_value = {"id": "ch-1", "default_model": "haiku"}
 
         route_message("ch-1", "user-1", "hello")
-        mock_send.assert_called_once_with("ch-1", "hello", model="haiku", on_text=None)
+        mock_send.assert_called_once_with("ch-1", "hello", model="haiku", on_text=None, voice_mode=False)
 
     @patch("src.router._get_channel_config")
     @patch("src.router._get_config")
@@ -283,7 +286,7 @@ class TestModelResolution:
         mock_get_config.return_value = mock_cfg
 
         route_message("ch-1", "user-1", "hello")
-        mock_send.assert_called_once_with("ch-1", "hello", model="opus", on_text=None)
+        mock_send.assert_called_once_with("ch-1", "hello", model="opus", on_text=None, voice_mode=False)
 
     @patch("src.router._get_channel_config")
     @patch("src.router._get_config")
@@ -297,7 +300,7 @@ class TestModelResolution:
         mock_get_config.return_value = mock_cfg
 
         route_message("ch-1", "user-1", "hello")
-        mock_send.assert_called_once_with("ch-1", "hello", model="sonnet", on_text=None)
+        mock_send.assert_called_once_with("ch-1", "hello", model="sonnet", on_text=None, voice_mode=False)
 
     @patch("src.router.get_active_session")
     @patch("src.router.send_message")
@@ -307,4 +310,4 @@ class TestModelResolution:
         mock_get_session.return_value = {"model": "opus", "session_id": "abc"}
 
         route_message("ch-1", "user-1", "hello")
-        mock_send.assert_called_once_with("ch-1", "hello", model="opus", on_text=None)
+        mock_send.assert_called_once_with("ch-1", "hello", model="opus", on_text=None, voice_mode=False)