rfx 2.0.0rc1

First release candidate of rfx 2.0. Install with pip install --pre rfx-fdtd (Python 3.11+, JAX 0.10). Plain pip install rfx-fdtd still installs the latest stable release.

What changes for a user in 2.0

• An input a solver path does not implement is refused, never dropped. run(), forward() and the S-parameter calculators raise before the first time step when the path your model is routed to does not solve a declared input — a conformal wall, subpixel smoothing, a lumped element, a port, a dispersive material, a plain source on an S-matrix request, a solver or precision request. In 1.x several of these ran a different model without a word.
• Validation is judged against a stated bar on a converged mesh: magnitudes within 2 dB, resonances and cutoffs within 1 %, electrical length within 1 % of the reference. See the support matrix and known limitations.
• Python 3.11 or newer. Python 3.10 users stay on 1.8.x.
• Multi-device (distributed) execution is not part of 2.0's supported set; it is planned for 2.1.

The full list of changes since 1.8.0 (128 entries) is assembled into CHANGELOG.md at 2.0.0; until then it is in changelog.d/.

How this candidate was checked

Cut from main 7ae97163 plus the version change (#1436). On that commit: the weekly scientific-validation lane (5 slow shards and the A6000 lane), the monthly cross-validation ladder, and the GPU suite (173 passed, 0 failed on an RTX 3090) all passed.

Known before 2.0.0: the ring-down settling witness can pass a record cut while a weakly coupled resonance still rings (#1426); documentation is brought up to date in one pass (#1171).