v0.23.0:0 - local / fine-tuned model support

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.

image/app/static/style.css

@@ -694,6 +694,7 @@ main {
 .card .repo a { color: inherit; text-decoration: none; }
 .card .repo a:hover { color: var(--info); text-decoration: underline; }
 .card .repo .hf-icon { font-size: 13px; opacity: 0.7; }
+.card .repo .local-path { font-family: var(--mono, ui-monospace, monospace); opacity: 0.85; }
 .tag {
   background: var(--surface-2);
   border: 1px solid var(--border);
@@ -738,6 +739,7 @@ main {
 .card .adv-btn,
 .card .test-btn { padding: 8px 12px; font-size: 12px; }
 .card .custom-pill { color: var(--info); border-color: rgba(96, 165, 250, 0.4); }
+.card .local-pill { color: var(--warn); border-color: rgba(245, 158, 11, 0.4); }
 .tag.on-disk { color: var(--accent); border-color: rgba(74, 222, 128, 0.4); }
 .tag.not-on-disk { color: var(--muted); border-color: var(--border); opacity: 0.7; }
 .card-actions .icon-btn.danger { color: var(--error); border-color: rgba(239, 68, 68, 0.3); margin-left: auto; }