Declare fdasrvf version floor (mv-SRVF code depends on >= 2.4.0 APIs)

[fabian-s]

The multivariate-SRVF code uses fdasrvf::multivariate_karcher_mean and multiple_align_multivariate, both reorganized in fdasrvf 2.4.0 ("all curve functions are under multivariate_karcher_mean"). This repo's tests run against fdasrvf 2.4.4.9000 — a development version. DESCRIPTION declares only bare Suggests: fdasrvf.

Consequence

A user with CRAN-fdasrvf-2.3.x passes rlang::check_installed("fdasrvf") and then gets a raw Error in do.call(...) : object 'multivariate_karcher_mean' is not exported from 'namespace:fdasrvf'.

Fix

1. Determine the exact minimum fdasrvf version that has the APIs used (likely 2.4.0; confirm).
2. Suggests: fdasrvf (>= 2.4.0) in DESCRIPTION.
3. rlang::check_installed("fdasrvf", version = "2.4.0") at each call site that uses the mv APIs (univariate srvf paths may have a lower floor).
4. Add a CI matrix entry pinned to the declared floor (e.g. install fdasrvf@v2.4.0 and run mv tests).

Found in the June-2026 ground-up review.