Simplify root CI to grouped-tests.yml (matrix from test/test_groups.toml) (#613)

Replace the hand-maintained group x version matrix (plus the bespoke GPU
job) in the root CI.yml `tests` job with the reusable grouped-tests.yml@v1
thin caller. The matrix now lives in test/test_groups.toml and is computed
by compute_affected_sublibraries.jl --root-matrix.

The root runtests.jl dispatches on the default GROUP env var, so no
group-env-name override is needed. check-bounds: auto is preserved as a
workflow-level input. coverage-directories defaults to src,ext (matches old).

Verified the computed root matrix equals the old workflow's (group, version,
runner) set exactly: 14/14.

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/CI.yml

@@ -18,45 +18,7 @@ concurrency:
 
 jobs:
   tests:
-    name: "Tests"
-    strategy:
-      fail-fast: false
-      matrix:
-        version:
-          - "lts"
-          - "1"
-          - "pre"
-        group:
-          - "Core"
-          - "QA"
-          - "SymbolicIndexingInterface"
-          - "Downstream"
-          - "NoPre"
-        exclude:
-          # JET (NoPre) is not run on prereleases.
-          - version: "pre"
-            group: "NoPre"
-          # QA (Aqua) runs only on lts and 1, never on prereleases.
-          - version: "pre"
-            group: "QA"
-    uses: "SciML/.github/.github/workflows/tests.yml@v1"
+    uses: "SciML/.github/.github/workflows/grouped-tests.yml@v1"
     with:
-      julia-version: "${{ matrix.version }}"
-      group: "${{ matrix.group }}"
-      num-threads: "2"
       check-bounds: "auto"
-      coverage-directories: "src,ext"
-    secrets: "inherit"
-
-  # GPU tests are a dep-adding group (test/GPU/Project.toml) that runs on the
-  # self-hosted GPU runner. Folded in from the former bespoke GPU.yml.
-  gpu:
-    name: "GPU Tests"
-    uses: "SciML/.github/.github/workflows/tests.yml@v1"
-    with:
-      julia-version: "1"
-      group: "GPU"
-      runner: '["self-hosted", "Linux", "X64", "gpu"]'
-      timeout-minutes: 60
-      coverage-directories: "src,ext"
     secrets: "inherit"

test/test_groups.toml

@@ -0,0 +1,24 @@
+[Core]
+versions = ["lts", "1", "pre"]
+num_threads = 2
+
+[QA]
+versions = ["lts", "1"]
+num_threads = 2
+
+[SymbolicIndexingInterface]
+versions = ["lts", "1", "pre"]
+num_threads = 2
+
+[Downstream]
+versions = ["lts", "1", "pre"]
+num_threads = 2
+
+[NoPre]
+versions = ["lts", "1"]
+num_threads = 2
+
+[GPU]
+versions = ["1"]
+runner = ["self-hosted", "Linux", "X64", "gpu"]
+timeout = 60