Require SciMLTesting 2.4

[ChrisRackauckas-Claude]

Ignore until reviewed by @ChrisRackauckas.

Summary

• require registered SciMLTesting 2.4 in the root test target
• require registered SciMLTesting 2.4 in the isolated QA environment
• preserve the existing narrow ExplicitImports allowlist and all SciMLTesting 2.4 defaults

Resolution evidence

Both test environments resolved SciMLTesting v2.4.0 from the registry. The package status showed [09d9d899] SciMLTesting v2.4.0 without a path or repository override.

Local validation

• GROUP=QA julia +release --project=. -e 'using Pkg; Pkg.test(; coverage = false)'
  • Julia 1.12.5
  • SciMLTesting v2.4.0
  • 19 passed, 1 existing justified broken allowlist, 20 total
  • completed in 9m42.4s
• julia +release --project=. -e 'using Pkg; Pkg.test(; coverage = false)'
  • Julia parser: 75/75
  • ANTLR parser: 138/138
  • error messages: 25/25
  • 238/238 assertions passed
• julia +release --project=../.runic_env -m Runic --check .
  • passed with exit 0

Process

No open PR from ChrisRackauckas-Claude covered this migration. The branch was created from SciML main at fab8c72; the fork was fast-forwarded first, and upstream had not moved before commit/push. No public API or rendered-doc changes were needed because SciMLTesting 2.4 strict QA passed as configured.