Add models that live as a directory on a Spark (e.g. LoRA-merged fine-tunes),
not just Hugging Face repos.
- ModelDef gains local_path; a model must set exactly one of repo / local_path.
The validator also enforces the local-path whitelist and that any
--chat-template lives inside local_path (only that dir is mounted).
- build_launch_command bind-mounts the dir into the vLLM container at the SAME
host==container path via the launch script's VLLM_SPARK_EXTRA_DOCKER_ARGS hook,
then `vllm serve <dir>`. No launch-cluster.sh change (verified the upstream
expands that var unquoted; contract noted in runbook.md).
- shellsafe.validate_local_path: absolute path, charset whitelist, no '.'/'..'.
- POST /api/models validates the full entry via ModelDef before persisting, so a
bad entry can't be written and then break catalog load; _merge_overrides skips
an invalid override entry instead of failing the whole catalog.
- disk.py size-probes a local path with du; disk-delete refused for local models.
- UI: "+ Add local model" dialog, `local` badge, path shown instead of an HF
link, delete button hidden for local models.
- Tests: local launch + injection round-trip, chat-template location, traversal,
exactly-one-source, _merge_overrides skip-invalid (94 pass). Reviewer-agent
pass; findings addressed.