chatterbox: switch health probe from /health (doesn't exist) to /api/model-info

devnen/Chatterbox-TTS-Server doesn't expose /health — neither in code
nor OpenAPI. The deploy hung on the playbook's `Wait for /health to
respond` loop indefinitely (each curl -> 404, retry forever) even
though the container was up and the model loaded clean to CUDA at
22:52:21 (~42s after start).

/api/model-info returns `{"loaded":true,...}` only after the model
finishes loading, so it doubles as liveness + readiness. Updated:

* compose.yaml healthcheck — grep for `"loaded":true` from
  /api/model-info.
* playbook wait step — same probe instead of /health.
* verify /health → verify /api/model-info reports loaded.
* verify /v1/audio/voices — switched from greping for `voice|alloy|echo`
  literals to parsing JSON and asserting the actual response shape:
  `{"status":"ok","voices":[...]}` (devnen's shape — note this is NOT
  the OpenAI list-format vibevoice uses).

stacks/chatterbox/compose.yaml

@@ -49,8 +49,11 @@ services:
       # is to use the in-image config + env var overrides.
       # - ${CHATTERBOX_CONFIG}:/app/config.yaml:ro
     healthcheck:
-      # Devnen wrapper exposes /health; the OpenAPI/docs path is /docs.
-      test: ["CMD-SHELL", "curl -fsS -o /dev/null http://localhost:8004/health || exit 1"]
+      # The devnen wrapper does NOT expose /health (no such route — use
+      # /docs or /openapi.json to enumerate). /api/model-info returns
+      # `{"loaded":true,...}` only after the model finishes loading,
+      # so it doubles as a liveness + ready probe.
+      test: ["CMD-SHELL", "curl -fsS http://localhost:8004/api/model-info | grep -q '\"loaded\":true' || exit 1"]
       interval: 30s
       timeout: 10s
       retries: 3