feat(lora-worker): stand up in-arbo LoRA training worker on irv-ml1 (arbo Phase 1 §4.1)

Host service (runs as llmuser, owns /opt/fluxgym + GPU access) that runs
sd-scripts SDXL LoRA training on demand for arbo — the infra-ops half of the
in-arbo LoRA training Phase 1 ownership split (vh/arbo
docs/contracts/in-arbo-lora-training-phase1.contract.md §4.1/§2).

- Fixed-invocation only (INV-T7): bounded params -> one sd-scripts command
  shape; every param range/allowlist/path-containment checked before spawn;
  bad request = 422, never a silent downgrade. 14 unit tests green.
- Thin supervisor: never imports torch; subprocesses the fluxgym venv's
  accelerate. 1-job-at-a-time (arbo lease is the serializer, 409 is backstop).
  Durable job records + boot reconciliation (§4.3).
- API: POST /train, GET /train/{id}[/log], POST /train/{id}/cancel,
  GET /gpu-status (per-device VRAM + tts_on_3090 co-OOM signal), GET /healthz.
- Wire-shape (§7 resolved with comfy-dev): shared /worktank/arbo/train handoff
  (group arbotrain, setgid 2770); worker binds 0.0.0.0:8203, arbo reaches via
  host.docker.internal:host-gateway (reachability proven on 172.20.0.1:8203);
  device-aware TTS steering via /gpu-status.

Deployed to irv-ml1 via playbooks/deploy-lora-training-worker.yaml (elway,
idempotent); systemd unit active; /healthz + /gpu-status verified live.

services/lora-training-worker/pyproject.toml

@@ -0,0 +1,26 @@
+[project]
+name = "lora-training-worker"
+version = "0.1.0"
+description = "Host service that runs sd-scripts LoRA training on demand for arbo (in-arbo LoRA training Phase 1, contract §4.1/§2). Fixed-invocation only (INV-T7)."
+requires-python = ">=3.11"
+dependencies = [
+    "fastapi>=0.115",
+    "uvicorn[standard]>=0.34",
+    "pydantic>=2.9",
+]
+
+[project.optional-dependencies]
+test = [
+    "pytest>=8.0",
+    "httpx>=0.27",  # fastapi TestClient
+]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["worker"]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]