docs(zonos-engine): capture the production ZONOS2 :1920 launch config (was live-only)

The Zonos TTS engine that zonos-gateway fronts (irv-ml1 3090, feeds asset-engine +
gateway-chat) ran as a bare native process with its real invocation existing ONLY
in the running process argv — the committed harness/zonos_server.sh on irv-ml1 was
STALE (said A6000/:1919, no perf flags; live is 3090/:1920 with cuda-graph/num-pages/
max-running-requests/memory-ratio). Captured the corrected canonical invocation +
tunables + the containerization plan here so the config survives a process death.

Engine = stock Zyphra/Zonos2 @ 194c0a3 (no custom PFI server code); torch 2.9.1+cu128;
15 GB HF weights. Next: containerize in-place on the 3090 (operator: keep off the
A6000, it OOMs under ComfyUI). Not yet built — this commit is the config capture only.

stacks/zonos-engine/zonos2-server.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+# CANONICAL launch invocation for the production ZONOS2 TTS engine (:1920, irv-ml1 3090).
+# Captured 2026-07-16 from the LIVE process argv — supersedes the stale
+# ~/tts-audition/harness/zonos_server.sh (which wrongly said A6000 / port 1919).
+# This is the reference invocation the container CMD encodes; it also works as a
+# direct native launcher until the container lands.
+#
+# Usage:
+#   zonos2-server.sh          # foreground
+#   zonos2-server.sh --bg     # detached, log to $ROOT/logs/zonos2_server.log
+set -euo pipefail
+
+ROOT="${ZONOS_ROOT:-/home/lkraven/tts-audition}"
+REPO="${ZONOS_REPO:-$ROOT/models/zonos2}"       # github.com/Zyphra/Zonos2 @ 194c0a3
+GPU_3090_UUID="GPU-12c15b3c-0827-0bab-b0cd-31aaa37a8e72"
+
+export CUDA_HOME="${CUDA_HOME:-/usr/local/cuda}"
+export PATH="$CUDA_HOME/bin:$PATH"
+export CUDA_VISIBLE_DEVICES="${CUDA_VISIBLE_DEVICES:-$GPU_3090_UUID}"  # 3090 (operator: keep off the A6000)
+
+cd "$REPO"
+CMD=(uv run python -m zonos2
+     --model-path "${ZONOS_MODEL:-Zyphra/ZONOS2}"
+     --host 0.0.0.0 --port "${ZONOS_PORT:-1920}"
+     --tts-default-voices-dir ./default_voices/
+     --cuda-graph-max-bs "${ZONOS_CUDA_GRAPH_MAX_BS:-1}"
+     --num-pages "${ZONOS_NUM_PAGES:-16384}"
+     --max-running-requests "${ZONOS_MAX_RUNNING_REQUESTS:-2}"
+     --memory-ratio "${ZONOS_MEMORY_RATIO:-0.3}")
+
+if [[ "${1:-}" == "--bg" ]]; then
+  mkdir -p "$ROOT/logs"
+  nohup "${CMD[@]}" > "$ROOT/logs/zonos2_server.log" 2>&1 &
+  echo "zonos2 engine started (bg) pid $! -> $ROOT/logs/zonos2_server.log"
+else
+  exec "${CMD[@]}"
+fi