feral v0.11.0

feral 0.11.0

Highlights

• Unsymmetric LU basis engine (feral::lu, #81) — general square
  A = P L U Q factorization with ftran/btran solves and simplex-style
  product-form column updates, auto-routing between a dense and a sparse
  engine. Exposed in Python as LuFactor.
• Expanded Python interface (all additive, backward-compatible):
  LuFactor; factor access via Solver.factors() (unit-lower L as
  CSC / optional scipy, block-diagonal D, perm/scaling for the
  L D Lᵀ = P (S A S) Pᵀ reconstruction); symbolic analysis via
  feral.analyze(...) / Solver.symbolic(); and introspection plus new
  Solver(...) tuning knobs (ordering, profiling, mc64_cache, …),
  pivot-magnitude and MC64 counters, last_factor_stats(),
  profile_report(), scaling_info.
• Documentation — new mdBook Python chapter sections, a new executed
  example notebook 05_lu_and_introspection, and a refreshed top-level
  README (LU engine, production-ready Status framing).

Packaging

• The six fill-reducing ordering crates (feral-ordering-core, feral-amd,
  feral-amf, feral-metis, feral-scotch, feral-kahip) are bumped
  0.2.0 → 0.2.1 so crates.io picks up the API-compatible fixes and perf
  work accumulated since 0.2.0 (they had been silently skipped at publish
  across 0.3.0–0.10.0). feral's version = "0.2" requirement resolves
  to 0.2.1 unchanged. A release-checklist guard now flags this staleness
  class so it cannot recur.

Correctness & performance campaign

This release also folds in the repo-review campaign: a large set of
correctness fixes (inertia reporting, MC64 partial-singular fallback,
sparse/dense LU singularity handling, MTX-reader validation, CSC validation,
2×2 D-block gating, static-pivot scale-invariance) and ordering-crate
algorithm fixes (real SHEM coarsening and true GGP gain in feral-metis,
vertex-weight flow balancing and n_components in feral-kahip,
separator-FM in feral-scotch, sorted-rows invariant in
feral-ordering-core), plus several performance improvements (pooled scratch
reuse, borrow-not-clone in feral_factor, linear default postorder).

See CHANGELOG.md
for the complete, itemized list (every fix is tagged with its finding ID).

Inertia remains validated against the feral + MUMPS 5.8.2 + SPRAL/SSIDS
consensus oracle; 705 tests passing.