- Sort harvested extras by filename so `mdcsum()` is reproducible
  across filesystems whose `read_dir` order differs. Without this,
  multi-replica deployments with byte-identical model dirs could
  publish different MDCs and thrash the frontend cache.
- Switch `with_context` error formatters from `{:?}` to `Path::display()`
  for consistency with surrounding code.
- Replace magic-5 capacity hint with `Self::TYPED_SLOT_COUNT` const
  so future slot additions touch one place.

Signed-off-by: nnshah1 <neelays@nvidia.com>

Worker harvest was using `HuggingFaceProvider::is_weight_file` from
mx, whose deny-list is narrower than the one used by the frontend's
gh-8749 hf-sibling harvest (#9610): mx misses `.gguf`, `.onnx`,
`.tflite`, `.pt`, `.pth`. That asymmetry meant a stray PyTorch /
ONNX / gguf weight in the model dir would slip past the worker
filter, get advertised as an `extra_files` entry, and ride the
metadata HTTP path to the frontend — turning a multi-GB weight
blob into a config-cache resident.

Promote `model_card::is_weight_file` to `pub(crate)` and call it
from the worker harvest. Single source of truth for "is this a
weight?" across both gh-8749 harvests; no new constants.

Bumps the worker harvest test to also assert `.pt` is filtered.

Signed-off-by: nnshah1 <neelays@nvidia.com>

Three dynamo-ops review threads on #9707:

1. Name-only LocalModel placeholders have an empty `full_path` and
   would fail on `read_dir("")` once self-host is enabled. Skip the
   harvest when `model_dir` isn't a directory.

2. `DirEntry::file_type()` and `DirEntry::metadata()` use lstat on
   Unix — they do not follow symlinks. HF snapshot dirs are full of
   symlinks pointing into `blobs/`, so we'd skip the very files we
   want to harvest. Switch to `Path::is_file()` which calls
   `fs::metadata` and follows symlinks.

3. `mdcsum()` previously omitted `extra_files`, so two workers with
   different siblings published the same checksum and the frontend
   cache served stale metadata. Hash each extra file's checksum in
   sorted order — sorting eliminates dependence on the harvest's
   filesystem-defined `read_dir` order.

Extends the harvest test fixture with a symlink-to-real-file and adds
a `returns_empty_for_missing_dir` test for the name-only path.

Signed-off-by: nnshah1 <neelays@nvidia.com>

…8749)

Extend the mocker self-host test to also `GET /v1/metadata/{slug}/_base/vocab.json` — `vocab.json` is a non-typed sibling
in the Qwen3 HF snapshot, so its presence in the route proves:

- `harvest_extra_files` picked it up
- the runtime registry registered it under `(slug, suffix, filename)`
- the system_status_server route serves it

Also exercises the symlink-follow fix from `048ba5af0c`: every entry
in HF snapshot dirs is a symlink into `blobs/`, so a non-following
stat would skip these files.

Signed-off-by: nnshah1 <neelays@nvidia.com>

- `move_to_self_host`: drop stale "(mx's deny-list)" attribution; the
  weight-file check now goes through `model_card::is_weight_file`.
- `mdcsum()`: compress the 6-line extras-hashing rationale to 3.

No behavior change.

Signed-off-by: nnshah1 <neelays@nvidia.com>