v0.7.0

• Add powerio-prob for complete numerical problem instances (#238). Its
  default build is matrix free; the matrix feature adds sparse projections,
  DC OPF bundle output.
• Move DC OPF instance types and bundle output out of powerio-matrix.
• Keep solver formulations and KKT operators outside powerio-prob.
• Demote powerio-json from the public case format surface (#229). It leaves
  the CLI format help and the generated format tables; pio_parse_str(..., "powerio-json", ...) and pio_to_format(..., "powerio-json", ...) keep
  working as ABI v4 compatibility aliases, and pio_to_json / pio_from_json
  are the documented balanced model JSON API.
• NetworkPackage::from_balanced is format neutral. Source adapters, such as
  GOC3 operating point extraction, run only for parsed reader input through
  from_parsed_balanced.
• Building a SCOPF instance from text requires an explicit source format.
• Add AC OPF problem instances (#248): powerio-prob gains AcOpfInstance
  and build_ac_opf_instance, carrying pi model branch data with separate tap
  and shift, per terminal charging, bus shunts, active and reactive demand,
  voltage bands, generator PQ bounds, and quadratic cost including the
  constant term (GenCost::quadratic_with_constant). Relaxations such as SOC
  forms consume the same instance. Matrix free; C ABI and Python exposure is
  #249.
• powerio-prob first publish review fixes: reserve membership sets now
  assign zone indices from the same document order as the reserve rows
  (sorted order previously crossed n_p/n_q between the two tables and
  diverged from src/goc3.jl past nine zones); a GOC3 branch with
  r = x = 0 is rejected by name instead of writing NaN into the wire
  rows; a missing device_type defaults to producer, the balanced
  reader's rule; the AC instance folds self-loop branch admittance into
  the bus shunt vectors, matching build_ybus; both instance builders
  reject a non-positive base MVA before scaling; the DC OPF bundle
  directory name stays confined to the output directory, and the bundle
  manifest reports the powerio core version (powerio::VERSION, new).
  SCOPF row structs and DcOpfOutputs are #[non_exhaustive].
• DSS reader: linecode= now sets a line's conductor count the way the
  engine's FetchLineCode does, the later of phases=/linecode= winning.
  A 4-wire line without an explicit phases= keeps its neutral instead of
  truncating the terminal map to 3 against a 4x4 linecode
  (frederikgeth/BMOPFTools.jl#332); thanks @frederikgeth

What's Changed

• Add C ABI construct/attach for operating point series by @samtalki in #239
• Add powerio-prob with matrix free DC OPF instances by @samtalki in #240
• Move GOC3 SCOPF instances into powerio-prob by @samtalki in #242
• Expose SCOPF instances over C and Python by @samtalki in #243
• Remove oversized GOC3 fixture and shorten C setter by @samtalki in #245
• DSS reader: take a line's conductor count from its linecode by @samtalki @frederikgeth in #247
• Enforce problem instance boundaries by @samtalki in #246
• Add AC OPF problem instances to powerio-prob by @samtalki in #251
• docs: rewrite public documentation for v0.7 by @samtalki in #244
• Fix powerio-prob review findings before the first publish by @samtalki in #253

Full Changelog: v0.6.3...v0.7.0