[ChrisRackauckas-Claude]

Please ignore this PR until it has been reviewed by @ChrisRackauckas.

What changed

Pure [compat] edits that drop older major versions of SciML packages. For each SciML dependency, only the current major remains (existing lower bound on that major is kept). No code, tests, or package version were changed.

• Project.toml [deps] OrdinaryDiffEqCore: 4 → 5 (drop 4; current SciML major is 5)

Why

Supporting multiple SciML majors keeps untested resolver windows. The current major is the one in the General registry; older majors are dropped even when that current major is recent.

Verification

Current majors come from JuliaRegistries/General Versions.toml. Not verified here: the full test suite, QA, or a live julia-downgrade-compat run.

[ChrisRackauckas-Claude]

OrdinaryDiffEqCore 5.0.0 and DiffEqDevTools 4.0.0 are yanked in General (they are the only releases of those majors). Compat "5" / "4" therefore admits no installable version — Pkg prints possible versions are: 1.0.0-4.14.3 for Core. Latest installable majors are OrdinaryDiffEqCore 4 and DiffEqDevTools 3. Pushed a fix that ignores yanked versions.

[ChrisRackauckas]

Closing as a no-op.

`OrdinaryDiffEqCore = "4"` was already the only major listed, so there was nothing older to drop. The original commit changed it to `"5"`, but OrdinaryDiffEqCore 5.0.0 is yanked = true in the General registry (the 4.x line is still the shipping one — 4.14.3 was released 2026-08-13). The follow-up commit correctly reverted that, which leaves this branch with no net change against master.