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>

vendor/discord-ext-voice-recv/VENDOR_INFO.md

@@ -1,22 +1,76 @@
 # Vendored: discord-ext-voice-recv
 
 **Upstream:** https://github.com/imayhaveborkedit/discord-ext-voice-recv
-**Pinned commit:** `ac04ea7b0941112e83767cf1c1469b408fa06748` (bump version 0.5.3a)
+**Pinned commit:** `ac04ea7b0941112e83767cf1c1469b408fa06748` (bump version 0.5.3a, master HEAD Jun 2025)
 **Vendored at:** 2026-05-27
+**Echo Core fork version:** `0.5.3a+echo.dave1` (PEP 440 local segment)
 **Reason:** Discord voice protocol is fragile, upstream is hobby fork. Adapter
 layer in `src/voice/_discord_voice_adapter.py` isolates upstream churn — if this
 package breaks, swap to py-cord by rewriting only that file.
 
-## Update procedure
+## Echo Core patch: `+echo.dave1` (DAVE E2E receive-side decrypt)
+
+### Why
+
+Discord enforces DAVE (E2E media encryption) on voice gateway `v=8` whenever the
+bot advertises `max_dave_protocol_version > 0` in IDENTIFY. discord.py 2.7.1 (the
+version Echo Core pins) does so unconditionally — Discord then closes the WS
+with code **4017** if the bot opts out by sending `max_dave_protocol_version=0`.
+DAVE is **mandatory**.
+
+Audio received from a DAVE-active room is **dual-wrapped**: transport layer
+(`aead_xchacha20_poly1305_rtpsize`) + DAVE E2E. Upstream voice-recv decrypts
+only the transport layer, then hands DAVE ciphertext to libopus, which raises
+`OpusError: corrupted stream` on every packet.
+
+### Patch shape
+
+~30 lines, all in `discord/ext/voice_recv/reader.py`:
+
+1. Module-level optional `davey` import (no-op when missing).
+2. `AudioReader._maybe_dave_decrypt(rtp_packet) -> Optional[bytes]` — gate logic
+   mirrors discord.py 2.7.1 send-side `can_encrypt` exactly. Returns the
+   DAVE-unwrapped payload, the original payload (DAVE inactive), or `None` to
+   drop the packet (unknown SSRC, decrypt failure).
+3. 4-line hook in `callback()` between transport-decrypt and `feed_rtp`:
+   overwrites `rtp_packet.decrypted_data` in place, or returns early to drop.
+
+The post-decrypt `is_silence()` check (formerly at reader.py:172) still works
+because we overwrite `decrypted_data` in place — silence frames produced by
+davey reach the existing check unchanged.
+
+### Dependency
+
+`davey==0.1.5` — matches discord.py 2.7.1 expectation. Pin in
+`echo-core/requirements.txt`. The import is optional at module level so tests
+and non-DAVE environments still run; the gate degrades to a bypass.
+
+### Re-sync strategy
+
+When upstream voice-recv adds DAVE support natively:
+
+1. Drop the three patch hunks in `reader.py` (davey import block,
+   `_maybe_dave_decrypt` method, hook in `callback()`).
+2. Revert `__version__` to upstream value in `__init__.py`.
+3. Update `Pinned commit` below.
+4. Run `pytest tests/test_voice_recv_dave.py tests/test_voice_adapter_contract.py`.
+
+The contract test `test_voice_recv_fork_version` asserts `__version__ ==
+'0.5.3a+echo.dave1'` and will fail fast on any accidental wipe during a careless
+upstream sync — forcing a conscious decision to either re-port or drop the
+patch.
+
+## Update procedure (vanilla upstream sync)
 
 ```bash
 cd vendor/discord-ext-voice-recv
 git fetch origin master
 git log HEAD..origin/master --oneline  # review what changed
 git checkout <new-commit>
+# RE-APPLY the +echo.dave1 patch if upstream still lacks DAVE
 cd ../..
 source .venv/bin/activate && pip install -e vendor/discord-ext-voice-recv --force-reinstall
-pytest tests/test_voice_adapter_contract.py -v  # MUST PASS — contract guard
+pytest tests/test_voice_adapter_contract.py tests/test_voice_recv_dave.py -v  # MUST PASS — contract + DAVE guards
 ```
 
 Update this file's `Pinned commit` after a successful upgrade.