Migrate CI to centralized SciML reusable workflows

[ChrisRackauckas-Claude]

Please ignore until reviewed by @ChrisRackauckas

Normalizes this repo's CI to the standard SciML reusable-workflow set, with every caller pinned at @v1 and secrets: inherit.

Workflows converted

• ci.yml (Tests) → calls SciML/.github/.github/workflows/tests.yml@v1. The full version × group matrix is reproduced exactly: groups Core, Autodiff, GPU, Downstream, Reactant, nopre; versions lts, 1, pre; with the same three excludes (nopre/pre, Downstream/pre, Reactant/pre). Coverage was collected in the original (codecov), so it stays on (reusable default). The original os: ubuntu-latest / arch: x64 were the reusable-workflow defaults, so they are inherited rather than restated.
• docs.yml (Documentation) → calls documentation.yml@v1. Original docs build did not collect coverage, so coverage: false.
• FormatCheck.yml (Runic) → calls runic.yml@v1. The repo already ran fredrikekre/runic-action, so this is a pure centralization; no source reformatting was required (verified locally with Runic v1.7.0, --check exit 0).
• SpellCheck.yml (typos) → calls spellcheck.yml@v1.
• downgrade.yml (Downgrade) → calls downgrade.yml@v1, preserving group Core, julia-version: 1.10, skip: Pkg,TOML, and allow-reresolve: false. The original paths-ignore: docs/** triggers are preserved.

Added

None — all five standard checks (Tests, Documentation, Runic, SpellCheck, Downgrade) already existed and were only centralized.

Not added (correctly absent)

No downstream/IntegrationTest, benchmark, or QA workflow existed, so none were invented. (Note: ci.yml has an in-repo Downstream test group driven by GROUP, which is preserved as a matrix group — it is not a separate downstream.yml workflow.)

dependabot.yml

• Removed the per-dependency crate-ci/typos ignore block (standing policy: keep everything current).
• github-actions block (/, weekly) and julia block (/, /docs, /test, daily, all-julia-packages group) preserved as-is.

CompatHelper

No CompatHelper.yml existed; nothing to remove.

TagBot

Left unchanged.

Typos findings

Ran typos (CLI 1.34.0) locally over the tree: clean, exit 0. The repo's .typos.toml (extend-word noth) covers the one known false positive. The centralized check uses typos 1.47.0 (newer than the previous 1.34.0 pin), which could surface additional findings; none are anticipated, but a newer typos version may flag items the older pin did not.

Heads-up for branch protection

Check names change with centralization (e.g. the test job name becomes Tests from the reusable workflow rather than Julia <ver> - <group> - <event>). Branch-protection required-status-checks must be updated to the new check names or required checks will appear missing.

🤖 Generated with Claude Code