v0.2.0

Changed

• Breaking: the sign convention of r_p. solve_tmm(..., polarization="p").r
  and fresnel_r(..., "p") now return r_p = (n1 cos2 - n2 cos1)/(n1 cos2 + n2 cos1),
  so r_p = r_s at normal incidence (air to glass: -0.2 instead of +0.2) and
  r_p -> +1 at grazing incidence. This is the opposite sign of Hecht / Born &
  Wolf; multiply by -1 to get the old values. t, R, T and A are unchanged.
  THEORY.md describes both conventions and why neither looks symmetric at both
  normal and grazing incidence.

Fixed

• THEORY.md formulas render correctly on GitHub: they use GitHub's protected
  math syntax, so Markdown no longer eats underscores and backslashes.

v0.1.0

First release.

Added

• solve_tmm(omega, layer_thickness, layer_n, ...): transfer-matrix method for
  planar multilayer stacks, s and p polarization at oblique incidence, absorbing
  layers and evanescent waves, returning a frozen Result (omega, r, t, R, T, A).
• num_substrate_passes for time-gated measurements, with a UserWarning when
  front-layer echoes beyond the implied gate exceed substrate_pass_tolerance.
• conjugate_model for the exp(+i omega t) time convention.
• Single-interface functions: fresnel_r, fresnel_t, fresnel_R, fresnel_T,
  critical_angle, brewster_angle, admittance, snell_cos_theta,
  snell_theta, and propagation_phase.
• Physical constants SPEED_OF_LIGHT, VACUUM_PERMEABILITY,
  VACUUM_PERMITTIVITY, VACUUM_IMPEDANCE.
• THEORY.md (derivation, conventions, substrate-pass validity), examples
  (antireflection coating, Fabry–Pérot slab, angle dependence), tests and a
  GitHub Actions workflow.
• examples extra installing cjcplot pinned to v0.2.0; the examples plot
  with cjcplot. pip install cjctmm itself stays numpy-only.