feat(lora-worker): Phase 2 publish-step — copy succeeded LoRA into ComfyUI loras + published_lora_name

On a train reaching succeeded, IN ADDITION to output/{name}.safetensors
(unchanged download source), COPY it into ComfyUI's loras search path at
/storetank/arbo/models/loras/trained/{train_id}/{name}.safetensors and
return published_lora_name (the ComfyUI-relative LoraLoader string) in the
terminal GET /train/{id} payload (arbo Phase 2 auto-registration, §4.1/§7).

- Copy not move; a publish failure NEVER fails the train (keeps succeeded,
  omits published_lora_name, logs the reason to the tailable run log).
- INV-T7-safe: a copy to a fixed computed path, no new free-form args.
- train_id derived from the handoff layout (output_dir.parent.name).
- Provisions loras/trained/ (arbotrain 2775, group-write per the Phase-1
  lesson; world-readable/traversable for ComfyUI) via the deploy playbook.
- ComfyUI verified to resolve nested loras subfolders (no flat fallback).
- Pure path helper unit-tested; 16 tests green.

services/lora-training-worker/worker/invocation.py

@@ -106,6 +106,16 @@ def validate_request(req: dict) -> dict:
     }
 
 
+def published_relative_path(output_dir: str, output_name: str) -> str:
+    """The ComfyUI-relative loras path for a succeeded LoRA (Phase 2 publish step).
+
+    Derives {train_id} from the handoff layout `HANDOFF_ROOT/{train_id}/output` — i.e. the
+    name of the dir the LoRA was written into. Returns e.g. `trained/392cf898ac03/name.safetensors`,
+    the exact string a ComfyUI `LoraLoader.lora_name` widget takes. Pure — no filesystem touch."""
+    train_id = Path(output_dir).parent.name
+    return f"{config.PUBLISH_SUBDIR}/{train_id}/{output_name}.safetensors"
+
+
 def build_command(req: dict) -> tuple[list[str], dict[str, str], dict]:
     """Validate `req` and return `(argv, env_overlay, params)` for the fixed sd-scripts invocation.