[docs] document scattering conventions and frozen-basis workflows

Update examples for sampled-interface tapers, explicit physical CPML spacing, copied SCPML widths, and the consolidated complex mode solver. Document breaking API changes, overlap measures, and PML convergence.

README.md

@@ -49,7 +49,7 @@ linear systems, ideally with double precision.
 
 **Requirements:**
 
-* python >=3.11
+* python >=3.12
 * numpy
 * scipy
 
@@ -118,11 +118,12 @@ python3 -m pytest -q | tee test_results.txt
 - `meanas.fdfd`: frequency-domain wave equations, sparse operators, SCPML, and
   iterative solves for driven problems.
 - `meanas.fdfd.waveguide_2d` / `meanas.fdfd.waveguide_3d`: waveguide mode
-  solvers, mode-source construction, and overlap windows for port-based
-  excitation and analysis.
-- `meanas.fdfd.waveguide_2d_complex`: targeted signed-`beta` waveguide modes,
-  transpose-left / Lorentz-dual projection fields, PML-mode diagnostics, and
-  overlap-based tracking for open cross-sections.
+  solvers, including targeted complex bases from the default half-sized
+  beta-squared or explicit signed-beta formulations, transpose-left and
+  Lorentz-dual projection fields on a shared field-array axis, separately
+  returned PML-mode diagnostics, overlap-based tracking,
+  mode-source construction, and overlap windows for port-based excitation and
+  analysis.
 - `meanas.fdtd`: Yee-step updates, CPML boundaries, flux/energy accounting, and
   on-the-fly phasor extraction for comparing time-domain runs against FDFD.
 - `meanas.fdmath`: low-level finite-difference operators, vectorization helpers,
@@ -175,7 +176,7 @@ The tracked examples under `examples/` are the intended entry points for users:
 - `examples/eme_bend.py`: straight-to-bent waveguide mode matching with
   cylindrical bend modes, interface scattering, and a cascaded bend-network
   example built with `scikit-rf`.
-- `examples/eme_taper_cmt.py`: sampled cross-section local-mode CMT for a
+- `examples/eme_taper_cmt.py`: sampled-interface EME with stable S cascading for a
   continuously varying rib-waveguide taper.
 - `examples/eme_taper_pml_modes.py`: targeted complex/PML mode solving,
   tracking, and construction of EME taper sections.