v0.5.0

• powerio-pkg: NetworkPackage is the one package type name (CompilerPackage
  is gone); the Julia binding already leads with NetworkPackage. The .pio.json
  format is unchanged.
• Python API: the seven module level package_* functions are replaced by the
  powerio.Package handle class, which parses the envelope once and exposes
  model_kind, operating_points(), materialize_operating_point(),
  as_balanced()/as_multiconductor(), validate(), validation(),
  diagnostics(), and the multiconductor to balanced preflight and lowering.
• .pio.json operating points: the per point label and duration_hours fields
  are gone; time_axis.labels and time_axis.duration_hours (indexed by
  points[].index) are the one source of truth. Readers ignore the old fields.
• Transmission formats: added GOC3 JSON input and Surge JSON read and write paths.
  GOC3 packages lift source time series into .pio.json operating_points,
  and package APIs can materialize one point into a static package.
• GOC3 reader fixes: branches with additional_shunt keep the line charging
  (b/2 per terminal added to the extra shunts, per the GO Challenge 3
  formulation); ta_lb/ta_ub map to an ActiveFlow transformer control
  range instead of fabricating angmin/angmax bus angle limits; producers
  and consumers honor initial_status.on_status like every other record type;
  object form section keys sort under a total order (mixed numeric and non
  numeric keys no longer risk a sort panic).
• powerio-pkg: GOC3 operating point extraction now consumes the parser's own
  document walking (device_rows, section, cost_at shared through a
  bridge), so update row indices match the payload by construction, including
  devices without a uid. A failed extraction attaches a
  READ.GOC3.OPERATING_POINTS_DROPPED diagnostic instead of silently
  producing a static only package. Materialized packages clear package_id
  (the parent id lives in origin.parent_package_id).
• PSS/E .raw: revision aware record layouts for v34/v35 transformer winding
  lines (twelve ratings, NODE), v35 generator records (NREG, BASLOD),
  and v35 switched shunts (NREG, per block status triples), on both read and
  write; the 2W/3W transformer split accepts float form K fields. The
  case14_v34.raw/case14_v35.raw fixtures are regenerated in the genuine
  layouts.
• PSLF .epc writer: parallel loads and shunts on one bus get distinct ids
  (extras["id"] preferred, positional fallback); the reader captures load,
  shunt, and SVD ids into extras["id"] so they survive cross format writes.
• PowerWorld .pwb: the table location search runs under a work budget, so a
  crafted file fails with a read error instead of pinning a core for hours.
• Surge JSON writer warns when named branch rating sets are dropped, like every
  other lossy writer.
• Writing a read only format (goc3-json) returns the new
  Error::WriteUnsupported instead of a misleading UnknownFormat.
• C ABI: the panic guard now covers index construction in the parse entry
  points; pio_package_validate documents its exclusive access requirement
  (the one non const entry point) and the header preamble scopes the
  concurrent read guarantee accordingly; PioDistNetwork gains the same
  compile time Send + Sync assertion as the other handles.
• SourceFormat::name() is the one source format name mapping; the package,
  CLI, and Python copies are gone.

What's Changed

• draft: v0.5.0/v1.0.0-alpha - prepare IR structs for stable construction by @samtalki in #169
• Add package operating points, GoC3, and Surge JSON support by @samtalki in #172

Full Changelog: v0.4.0...v0.5.0