feat: downloader for Qwen-Image weights, switch-model.sh script

Two frontier tickets from the ComfyUI map (#38), both unblocked now
that their blockers (#39 model choice, #40 lazytainer research) are
resolved.

- downloader-comfyui service (docker-compose.yml) + COMFYUI_* vars
  (.env.example): fetches Qwen-Image FP8 diffusion/text-encoder/VAE
  weights from Comfy-Org/Qwen-Image_ComfyUI, same test -f guard
  pattern as the existing downloaders. Closes #42.
- scripts/switch-model.sh: swaps GPU residency between llama-server
  and comfyui via direct `docker compose stop`/`up -d`, bypassing
  lazytainer per docs/research/lazytainer-omniroute-idle-stop.md
  (its packet-threshold detector can't distinguish OmniRoute's health
  checks from real traffic, so idle-stop can't be relied on for a
  deliberate swap). llama-server-fast stays resident throughout —
  not part of this swap. Closes #43.
- scripts/update.sh: runs the new downloader profile.

docker compose config -q validated clean.

Refs #38, #42, #43

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MrnMEdzeQzqZE5soVEXPCx

scripts/switch-model.sh

@@ -0,0 +1,56 @@
+#!/usr/bin/env bash
+# Swap GPU residency between llama-server (Qwen) and comfyui — they never
+# run concurrently, VRAM doesn't fit both (see issue #38's map). Manual
+# invocation only, no auto-switching.
+#
+# Bypasses lazytainer entirely and drives docker compose directly — its
+# idle-stop can't be used for this. Root cause (see
+# docs/research/lazytainer-omniroute-idle-stop.md, issue #40): lazytainer's
+# packet-threshold detector is source-blind and can't tell OmniRoute's
+# periodic health-check pings apart from real traffic on the same port, so
+# it never reliably sleeps a service on its own. A scripted swap always
+# knows which service should go up/down, so it doesn't need that heuristic.
+#
+# llama-server-fast (the small classifier model, issue #44) is NOT part of
+# this swap — it's meant to stay always-resident. Worst case with comfyui up
+# is comfyui (~25GB, Qwen-Image FP8) + llama-server-fast (~5GB) ≈ 30GB,
+# still under the 32GB card but tight — unverified on real hardware, check
+# `docker compose ps` / VRAM usage after the first real swap.
+#
+# OmniRoute may show the just-stopped provider as errored/offline in its
+# dashboard for up to CREDENTIAL_HEALTH_CHECK_INTERVAL (default 5 min) after
+# a swap — cosmetic, not a functional problem (see the research doc above).
+set -euo pipefail
+cd "$(dirname "$0")/.."
+
+usage() {
+  echo "Usage: $0 {qwen|comfyui}" >&2
+  echo "  qwen    - stop comfyui, start llama-server" >&2
+  echo "  comfyui - stop llama-server, start comfyui" >&2
+  exit 1
+}
+
+[ $# -eq 1 ] || usage
+
+case "$1" in
+  qwen)
+    from=comfyui
+    to=llama-server
+    ;;
+  comfyui)
+    from=llama-server
+    to=comfyui
+    ;;
+  *)
+    usage
+    ;;
+esac
+
+echo "==> stopping $from"
+docker compose stop "$from"
+
+echo "==> starting $to"
+docker compose up -d "$to"
+
+echo "==> status"
+docker compose ps

scripts/update.sh

@@ -89,6 +89,7 @@ docker compose build --pull
 echo "==> ensuring models are downloaded (skips already-present files)"
 docker compose --profile tools run --rm downloader
 docker compose --profile tools run --rm downloader-fast
+docker compose --profile tools run --rm downloader-comfyui
 
 echo "==> bringing up omniroute"
 docker compose up -d --wait omniroute