v0.1.0-alpha0 — first alpha release

First alpha release. Base engine is pip-installable, imports cleanly in a
fresh virtualenv, ships with 100 passing tests, and reproduces two
published benchmarks (Horton 2012 Table VII and Boteler 1997 DSTL) at
sub-1 % relative error.

Added

• Sources: SyntheticSource (Gaussian, step, sinusoid), plus
  INTERMAGNETSource (IAGA-2002) and SuperMAGSource (CSV) with
  XYZF/HDZF frame conversion and sentinel handling.
• Earth: Layered1D (Wait 1954 recursion, matches uniform half-space
  analytic at rtol=1e-12), model registry (get_model("quebec_7layer")
  etc.), CoastalCorrection2D (Boteler-Pirjola-style TE/TM interpolation
  → TensorImpedance).
• Impedance: full Impedance ABC + ScalarImpedance (with HDF5
  roundtrip) + TensorImpedance (2×2 tensor per frequency, HDF5, apply,
  reduces to ScalarImpedance in the anti-diagonal limit).
• Network: PowerGridNetwork with MATPOWER-GMD (epri21.m) loader
  handling the "row-position vs AC-bus" quirk; PipelineNetwork with
  DSTL equivalent-π discretisation.
• Solver: LPMSolver with delta-winding-safe active-subspace solve;
  Solver.solve() ABC signature accepts the ConductorNetwork.
• Devices: TransformerModel port of Mate 2021 top-oil + hot-spot
  (bilinear/Tustin discretisation, ThermalParams). DeviceResponse
  extended with top_oil_C / hotspot_C fields.
• Geo: WGS84 projection helpers (meridian_radius_m,
  prime_vertical_radius_m, latlon_to_local_xy_wgs84_m) — networks now
  use per-segment WGS84 line integrals matching Horton (2012) Appendix.
• UQ: Uncertain[T] generic + propagate_uncertainty MC.
• I/O: schema-versioned HDF5 reader/writer, MATPOWER-GMD parser,
  IAGA-2002 parser.
• CLI: geopulse run|validate|info|earth list.
• Benchmarks: Horton 2012 EPRI21 test case + expected_gic.csv from
  paper Table VII; passing test at rtol=1e-2.
• Examples: 01_first_gic.py (Gaussian pulse smoke test),
  04_pipeline_dstl.py (DSTL vs analytic profile),
  05_transformer_hotspot.py (Mate 2021 hot-spot reproduction).
• Packaging: py.typed marker; wheel + sdist build clean via
  python -m build; installs in a fresh venv.
• Docs: Sphinx scaffold with logo + favicon.

Deferred (stubs raise NotImplementedYetError with WP reference)

• CableNetwork (WP2), RailwayNetwork (WP4).
• MNASolver (WP3), PySpiceSolver (WP3).
• RectifierModel, CathodicProtectionModel, harmonics (WP3).
• KernelImpedance + Unstructured3D (WP3).
• Structured2D full FD MT solver (WP-future — CoastalCorrection2D
  is the pragmatic stand-in).
• metrics/* summary statistics (WP2/3/4).
• viz/* plotting helpers (WP1/2).