feat(zonos): OpenAI-ish REST adapter for asset-engine routing

Upstream Zonos ships only Gradio + Python SDK — no REST surface — so
asset-engine (which routes a clean JSON POST to /v1/audio/speech) can't
target it directly. Add a thin FastAPI adapter (stacks/zonos/adapter/):
POST /v1/audio/speech in front of the Zonos SDK, built FROM local/zonos
to reuse torch/CUDA/SDK. Returns a JSON envelope {audio, audio_format,
seed} — the seed rides back so asset-engine regenerate/fork can pin it
(Zonos is the fleet's first genuinely seedable TTS). compose gains a
zonos-api service on 8201; .env.example gains the port + voices dir.

stacks/zonos/.env.example

@@ -16,9 +16,14 @@ ZONOS_TAG=v1
 # Reserved on irv-ml1: 8188 ComfyUI, 8190 CosyVoice, 8191 Qwen3-TTS,
 # 8192 IndexTTS-2, 8193 Kokoro, 8194 VibeVoice, 8195 Fish-S2,
 # 8196 Chatterbox, 8197 Voxtral, 8198 Kyutai, 8200 Dia, 8765 Parakeet.
-# 8199 picked here.
+# 8199 picked here for the Gradio eval UI.
 ZONOS_PORT=8199
 
+# Host port for the OpenAI-ish REST adapter (zonos-api service) that
+# asset-engine routes to. Container listens on 8000 internally. 8201 is
+# the next free slot above the Gradio port.
+ZONOS_API_PORT=8201
+
 # Bind address. 0.0.0.0 exposes on all interfaces (incl. WG tunnel
 # interface 10.100.79.3); 127.0.0.1 restricts to local-only.
 ZONOS_BIND=0.0.0.0
@@ -42,3 +47,12 @@ ZONOS_GPU_DEVICES=0
 # Bind-mounted so they survive container recreate. Excluded from restic
 # (regenerable from HF).
 ZONOS_CACHE_DIR=/worktank/zonos/cache
+
+# Reference voice clips for zero-shot cloning (mounted read-only into the
+# adapter at /app/voices). Drop 10–30s clean WAVs here; the catalog's
+# `voice` field selects one by filename. Empty/absent → default voice.
+ZONOS_VOICES_DIR=/worktank/zonos/voices
+
+# Model the adapter loads at startup. Only the transformer variant is
+# available in the current image (mamba-ssm absent → no hybrid).
+ZONOS_MODEL=Zyphra/Zonos-v0.1-transformer