The v2.0 baseline. Single disk-first chain (run_cp -> apply_filters
-> run_cf / run_cm / run_ce), single combined stats.{h5,xdmf}, no
input mutation, multi-format mesh resolver, embedded
/processing_metadata, opt-in normalize_time, required nominal_area /
nominal_volume, first-class filter chain, dependency footprint
trimmed and floors raised, public-API surface trimmed to a single
pipeline.

See docs/source/release_notes.md for the full v2.0.0 changeset
(breaking changes, migration notes, dep bumps).