Canonical CI: grouped-tests.yml + root test/test_groups.toml

[ChrisRackauckas-Claude]

Summary

Converts the root test workflow .github/workflows/Tests.yml to the canonical thin caller SciML/.github/.github/workflows/grouped-tests.yml@v1, declaring the group × version matrix once in a ROOT test/test_groups.toml.

The package already dispatches Core / NoPre groups via the GROUP env var in test/runtests.jl (Category A), so no runtests.jl change was made. NoPre runs the QA (Aqua) + JET checks, guarded by isempty(VERSION.prerelease) in runtests.jl.

Changes

• .github/workflows/Tests.yml: matrix test job replaced by the thin caller. Filename and name: "Tests" are unchanged so branch-protection status checks are preserved. on: triggers (pull_request / push / schedule, paths-ignore: docs/**) and concurrency: are preserved verbatim.
• test/test_groups.toml (new, repo root): declares the matrix.

[Core]
versions = ["lts", "1", "pre"]

[NoPre]
versions = ["lts", "1", "pre"]

No with: inputs were needed: the old caller used tests.yml@v1 defaults throughout (GROUP env var, check-bounds: yes, coverage on, coverage-directories: src,ext), all of which are the defaults of grouped-tests.yml@v1.

Matrix match — 6/6 exact

compute_affected_sublibraries.jl --root-matrix (from SciML/.github@v1) emits exactly the previous workflow's cross product:

group	versions
Core	lts, 1, pre
NoPre	lts, 1, pre

Old workflow: group ∈ {Core, NoPre} × version ∈ {1, lts, pre} = 6 cells. Emitted: the same 6 (group, version) pairs, all runner: ubuntu-latest (Linux-only; no os field added). Group names are passed verbatim to GROUP, preserving the existing runtests.jl dispatch.

QA

Category A: existing QA (Aqua + JET) already wired via the NoPre group; static matrix-verify only, no local QA run. TOML and YAML both parse cleanly.

Ignore until reviewed by @ChrisRackauckas.