v4.1.0 — the rsig half of the cohort corpora

The rsig half of the two new cohort corpora. rsig_synthetic-blood.npz and
rsig_synthetic-tissue.npz ship beside the naive and memory pair — four corpora, all synthetic,
none needing a cohort sample.

pip install -U mirpy-lib
mir signature --corpus synthetic-blood cohort/*.tsv.gz -o rsig.tsv

Requires vdjtools >= 4.1.0, which is where the draw lives: one corpus_plan resolves a corpus
name for both halves and one corpus_meta writes both manifests, so a vsig_<name>/rsig_<name>
pair cannot disagree about the cohort, the three measured ladders, the rank correlations or the
germline it was drawn from — which is what makes joining them on sample_id mean anything (947 + 904
-> 1,852 columns, verified on real samples).

Each repertoire is a naive/memory mixture drawn across three quantile ladders measured per locus on
the compartment it is named after: clonotype richness, reads per expanded clone, and the singleton
fraction that stands in for the naive share. The construction, why reads per expanded clone is the
drawable quantity, and the acceptance table are in the
vdjtools 4.1.0 notes. The short
version: naive and memory draw depth over 2.4x-11.0x per locus, while real blood TRB richness
spans 43x (74 to 3,162 clonotypes, n = 34,365 samples) and tissue IGH 259x — and a corpus estimates
its bounds, centre and per-PC scaling from its own draw, none of which extrapolates.

Changed

• mir.signature.synthesize's first parameter is corpus_name, not regime, and mir corpus --corpus takes all four names. --size defaults to auto; --depth-spread is new and is refused
  on a synthetic-* corpus rather than silently ignored, because that band is measured.
• The rsig manifest now carries depth_spread, depth_spread_requested, cohort, richness_band,
  expanded_count_band, singleton_frac_band and rank_corr. It previously carried no depth
  field at all, which left the one thing a reader needs in order to know whether a corpus covers
  their samples readable only from the vsig half. A new test asserts the two halves' manifests agree
  key by key.

Full changelog: https://github.com/antigenomics/mirpy/blob/master/CHANGELOG.md