feat(voice): DAVE E2E receive-side decrypt — unblocks Pas 12

Vendored fork: discord-ext-voice_recv 0.5.3a+echo.dave1

Patches the receive pipeline to handle Discord's mandatory DAVE E2E
encryption on voice gateway v=8. Without this, opus_decode raised
"corrupted stream" on every received packet in a DAVE-active room and
voice-to-voice never connected.

DAVE patch (vendor/discord-ext-voice-recv/reader.py):
- `_maybe_dave_decrypt(rtp_packet)`: gate mirrors discord.py 2.7.1
  `voice_state.can_encrypt`. Uses davey's `can_passthrough(user_id)` to
  branch — peers in passthrough send transport-only packets that pass
  through verbatim; peers in DAVE epoch go through `davey.decrypt`.
- Hooked in `callback()` between transport decrypt and feed_rtp;
  drops on decrypt failure without killing the reader thread.
- Bumps __version__ to '0.5.3a+echo.dave1' (PEP 440 local segment) so a
  contract test can fail fast on accidental upstream-sync overwrite.

Pipeline fixes uncovered while testing DAVE end-to-end:
- src/voice/pipeline.py: silero-vad v6+ requires exactly 512 samples per
  call at 16kHz; our 100ms window (1600 samples) was silently raising
  ValueError → VAD always returned False → STT never fired. Slice the
  window into 512-sample chunks. Bump whisper beam_size 1→5 and add a
  Romanian `initial_prompt` — transcriptions go from "Eco salt." gibberish
  to "Echo, salutare, te rog spune-mi cât este ora."
- src/voice/tts_stream.py: EchoStreamingAudioSource.read() returns a 20ms
  silence frame instead of b'' on empty queue. Empty return is treated
  by Discord as end-of-stream and kills the player, so any TTS pushed
  later would be silently discarded.
- src/adapters/discord_voice.py: actually attach EchoStreamingAudioSource
  to the voice client after the wakeup beep (chained via `after=`),
  which was missing entirely — TTS frames had no consumer.

Tests:
- tests/test_voice_recv_dave.py: 11 unit + callback integration tests
  covering bypass paths, can_passthrough gate, decrypt error handling.
- tests/test_voice_adapter_contract.py: +test_voice_recv_fork_version
  and +test_voice_connection_state_has_dave_attrs guards against
  upstream drift on either side.

Config:
- config.json: voice.allowed_user_ids whitelist for Marius's user id.

Status: voice-to-voice loop closes end-to-end (DAVE → VAD → Whisper →
Claude → Supertonic → audio out). Latency is ~8-13s per turn, which is
out of scope for this commit — see TODOS.md for the real-time UX
follow-up plan.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tests/test_voice_adapter_contract.py

@@ -169,3 +169,54 @@ def test_voice_data_has_opus_property():
 
     opus_attr = inspect.getattr_static(VoiceData, "opus", None)
     assert isinstance(opus_attr, property), "VoiceData.opus must be a property"
+
+
+# --- Echo-core DAVE-decrypt fork guards -------------------------------------
+#
+# Two contract tests pinned by the DAVE receive-side decrypt patch.
+# See plan: /home/moltbot/.claude/plans/wiggly-exploring-glade.md
+#
+# These fail fast on either:
+#   1. An upstream voice-recv re-install wiping the fork's version marker
+#      (i.e. our patch is gone), OR
+#   2. A discord.py upgrade renaming the connection-level DAVE attrs the
+#      patch reads (`dave_session`, `dave_protocol_version`).
+
+
+def test_voice_recv_fork_version():
+    """Echo-core fork tag for the DAVE-decrypt patch.
+
+    Lane A bumps `voice_recv.__version__` to `'0.5.3a+echo.dave1'` (PEP 440
+    local segment). If this assertion fails after a vendor reinstall, the
+    fork patch has been lost — re-apply `_maybe_dave_decrypt` + the
+    `callback()` hook before deploying, or live voice will regress to the
+    `opus_decode: corrupted stream` error chain.
+    """
+    from discord.ext import voice_recv
+
+    assert voice_recv.__version__ == "0.5.3a+echo.dave1", (
+        f"voice_recv.__version__ is {voice_recv.__version__!r}; expected "
+        "'0.5.3a+echo.dave1'. The DAVE-decrypt fork patch has been "
+        "overwritten — re-apply before reinstalling the vendored package."
+    )
+
+
+def test_voice_connection_state_has_dave_attrs():
+    """`_maybe_dave_decrypt` reads `dave_session` and `dave_protocol_version`
+    off the discord.py `VoiceConnectionState`. If a future discord.py upgrade
+    renames either attr, fail loudly here rather than in a live voice call
+    (where the symptom is silent packet drops).
+    """
+    from discord import voice_state
+
+    src = inspect.getsource(voice_state.VoiceConnectionState)
+    assert "dave_session" in src, (
+        "discord.voice_state.VoiceConnectionState source no longer mentions "
+        "'dave_session' — discord.py may have renamed the attr. Update "
+        "vendor/discord-ext-voice-recv/.../reader.py::_maybe_dave_decrypt."
+    )
+    assert "dave_protocol_version" in src, (
+        "discord.voice_state.VoiceConnectionState source no longer mentions "
+        "'dave_protocol_version' — discord.py may have renamed the attr. "
+        "Update _maybe_dave_decrypt accordingly."
+    )