Canonical CI: grouped-tests.yml + root test/test_groups.toml (#57)

Convert the root Tests.yml test job to the canonical thin caller of
SciML/.github grouped-tests.yml@v1, with the group x version matrix
declared once in test/test_groups.toml. The runtests.jl GROUP dispatch
(Core/nopre) already exists, so no test-runner change is needed.

The emitted root matrix reproduces the old hand-maintained matrix exactly
(5/5): Core on {lts,1,pre} and nopre on {lts,1}.

Co-authored-by: ChrisRackauckas-Claude <accounts@chrisrackauckas.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: 3 people

.github/workflows/Tests.yml

@@ -18,26 +18,6 @@ concurrency:
   cancel-in-progress: ${{ github.ref_name != github.event.repository.default_branch || github.ref != 'refs/tags/v*' }}
 
 jobs:
-  test:
-    name: "Tests"
-    strategy:
-      fail-fast: false
-      matrix:
-        group:
-          - Core
-          - nopre
-        version:
-          - '1'
-          - 'lts'
-          - 'pre'
-        arch:
-          - x64
-        exclude:
-          - version: 'pre'
-            group: 'nopre'
-    uses: "SciML/.github/.github/workflows/tests.yml@v1"
-    with:
-      group: "${{ matrix.group }}"
-      julia-version: "${{ matrix.version }}"
-      julia-arch: "${{ matrix.arch }}"
+  tests:
+    uses: "SciML/.github/.github/workflows/grouped-tests.yml@v1"
     secrets: "inherit"

test/test_groups.toml

@@ -0,0 +1,5 @@
+[Core]
+versions = ["lts", "1", "pre"]
+
+[nopre]
+versions = ["lts", "1"]