- ds4 kv janitor: a checkpoint is deleted only when ALL hold — untouched by
  max(mtime, atime) for the age (so a checkpoint ds4 merely READS, which bumps
  atime not mtime, is spared); not currently open (fd/mmap) by a ds4-server;
  and ds4 is not serving any request. New in-flight counter on Ds4Backend
  (any_request_active) gates the sweep.
- settings: "Download a default DeepSeek V4 model" — select + button backed by
  new /admin/api/ds4/default-models catalog (q2-imatrix / q2-q4 / q4 / mtp from
  antirez/deepseek-v4-gguf). Reuses the normal downloader, which flattens the
  gguf into the cache and surfaces it in the model list; live progress.
- parser: rescue the degraded plaintext <tool>name arg: value</tool> form that
  heavy quants (ds4 q2-imatrix) emit when they can't reproduce DSML. Scoped to
  DeepSeekParser only (never the shared ToolCallParser, so other families are
  untouched), requires a DECLARED tool name, plaintext-only inner, and the
  block(s) to be the message's trailing action — so a <tool> example inside a
  prose reply is not misread as a call.
- settings: corrected ds4 perf note (i-quants/Q2_K fail CUDA prefill; use Q4_K+).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>