ci: uniformize onto centralized CI (project-model SublibraryCI + cleanup) (#3718)

* ci(SublibraryCI): move to centralized project-model workflow

Switch from sublibrary-tests.yml (GROUP-dispatch via root runtests.jl) to the
centralized project-model sublibrary-project-tests.yml, which now carries the
full test_groups.toml matrix (multi-version, GPU/threaded groups on custom
runners, per-group timeout/num_threads/local_only) plus the same dependency-
graph change detection. Each lib/X is tested via tests.yml project=lib/X with
the group passed as ODEDIFFEQ_TEST_GROUP and check_bounds=auto, matching what
the root dispatcher did.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* ci: uniformize — add-DocPreviewCleanup

Part of bringing this repo onto the full centralized CI setup (SciML/.github
@v1): remove retired CompatHelper (Dependabot drives [compat]) and/or add the
centralized Documenter preview cleanup.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

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/DocPreviewCleanup.yml

@@ -0,0 +1,17 @@
+name: Doc Preview Cleanup
+
+on:
+  pull_request:
+    types: [closed]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: write
+
+jobs:
+  doc-preview-cleanup:
+    uses: "SciML/.github/.github/workflows/docs-preview-cleanup.yml@v1"
+    secrets: "inherit"

.github/workflows/SublibraryCI.yml

@@ -13,5 +13,8 @@ concurrency:
   cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
 jobs:
   sublibrary-ci:
-    uses: "SciML/.github/.github/workflows/sublibrary-tests.yml@v1"
+    uses: "SciML/.github/.github/workflows/sublibrary-project-tests.yml@v1"
+    with:
+      group-env-name: ODEDIFFEQ_TEST_GROUP
+      check-bounds: auto
     secrets: "inherit"