test: spell out SupernodalLU threshold variable

[ChrisRackauckas-Claude]

Ignore this PR until it has been reviewed by @ChrisRackauckas.

Summary

Rename the local thr loop variable in the SupernodalLU dense-kernel tests to threshold so Typos does not interpret it as a misspelling.

Regression evidence

• Clean current main (ed7bcb014f03d15f50e9a5cf86f8a314ab2d248d) reports exactly two Typos 1.48.0 findings at test/Core/supernodal_lu.jl:176-177.
• An automated bisect identified 4c58ce272a79969d45eaa640bdf74c2a437263bf (SupernodalLU: fix block factorization on the direct-BLAS backends #1119) as the first bad commit.

Local verification

The rebased #1124 tree is byte-identical to the separately tested current-main validation tree (a11cb43039569967e2bd97e862cf6b32a5b1ba5c):

• GROUP=Core JULIA_NUM_THREADS=2 julia +1.12 --project=. -e 'using Pkg; Pkg.test()' — passed: 2,299 assertions plus three pre-existing broken cases; SupernodalLU internals passed 72/72.
• Typos 1.48.0 over the whole repository — passed with zero findings.
• Runic over the changed file and whole repository — passed.
• git diff --check — passed.

The remote branch was audited before the lease-protected rebase push; it contained only the prior bot-authored version of this same commit.

[ChrisRackauckas-Claude]

Scratchpad plan and evidence:

1. Reproduced the spellcheck failure on exact clean main at fd8271c19613be69afba209e5f117c29f162f8a4 with the same typos 1.48.0 release used by CI: exactly two diagnostics, both for thr in test/Core/supernodal_lu.jl.
2. Verified the exact parent ae3cf086bf8c590002f92f6195600cdfe9d8304e passes, identifying 4c58ce272a79969d45eaa640bdf74c2a437263bf as the introducing commit.
3. Applied the minimal semantic-preserving rename thr → threshold at declaration and use.
4. Re-ran typos 1.48.0 and whole-repository Runic 1.5.1: both exited 0.
5. Ran the official GROUP=Core suite on Julia 1.12: Testing LinearSolve tests passed; affected SupernodalLU testset was 72/72.

No test was skipped, disabled, or loosened.

[ChrisRackauckas-Claude]

CI triage update: OrdinaryDiffEq.jl/InterfaceII fails during Pkg.develop, before tests, because current LinearSolve 5.3.0 is incompatible with the LinearSolve range in OrdinaryDiffEqDefault 2.x. I reproduced the identical resolver failure locally using exact clean LinearSolve main (fd8271c19613be69afba209e5f117c29f162f8a4) and exact current OrdinaryDiffEq master (938dae56bf1051758d7b49b78eda0fffc2463d3b) on Julia 1.10.11. The prior #1123 run has the same 29-second failure. This predates and is independent of this PR local-variable rename; it is queued as a separate clean-main investigation.

[ChrisRackauckas-Claude]

Resolver follow-up ownership/status: no additional OrdinaryDiffEq code PR is needed. SciML/OrdinaryDiffEq.jl#3991 is already merged and superseded closed #3984 verbatim. The clean-main downstream resolver remains blocked while the corresponding General registrations are pending: JuliaRegistries/General#162154 (OrdinaryDiffEqDefault v2.4.0) and JuliaRegistries/General#162158 (OrdinaryDiffEqFIRK v2.5.0). The staged registry metadata has been reproduced separately as resolving/importing with LinearSolve 5.3.1; its exact Core validations are still running. This remains independent of #1124.

[ChrisRackauckas-Claude]

Resolver status update: JuliaRegistries/General#162154 (OrdinaryDiffEqDefault v2.4.0) and JuliaRegistries/General#162158 (OrdinaryDiffEqFIRK v2.5.0) are now merged. The four downstream failures in the completed run predate those registrations. I attempted to rerun failed jobs through the Actions API, but this credential lacks upstream repository Actions-admin permission (403 Must have admin rights). I did not add an empty commit merely to retrigger CI; these jobs should be rerun by a maintainer.

[ChrisRackauckas-Claude]

Terminal CI checkpoint for rebased head 79b618e33b: 55 checks succeeded, 4 were skipped, and 3 failed. None is caused by the two-line thr → threshold test rename.

• Documentation: the build reached Documenter and stopped only in linkcheck. The MIT adjoint PDF timed out at the job's 10-second curl limit, and the LLNL Hypre page returned HTTP 500. I rechecked both URLs locally after the run with a 30-second limit; both returned HTTP 200 (0.11 s and 0.47 s respectively). I did not change or silence linkcheck.
• ModelingToolkit/All: the exact PR job reports 758 passed, 11 errors, and 14 pre-existing broken cases. Running the same integration test against exact clean LinearSolve main produces the identical 758/11/14 result with the same dependency graph. Nine errors are DelayDiffEq resolver/runtime fallout addressed by the separately tested General compatibility PR Retroactively cap DelayDiffEq at OrdinaryDiffEqCore 4.8.0 JuliaRegistries/General#162781; the remaining two clean-main initialization errors are under a separate reproduce/bisect investigation.
• SciMLSensitivity/Core1: resolution is impossible because the tested source requires SciMLBase 3.40 while General currently ends at 3.39.1. The SciMLBase 3.40 registry transition is not complete; the prerequisite compatibility-cap PR Retroactively cap SciMLBase at 3.39 for packages that lose reexported names JuliaRegistries/General#162635 remains open.

The branch-specific checks, including Typos, Core, Runic, and the affected SupernodalLU testset, are green. This PR remains a focused clean-main typo fix.

[ChrisRackauckas-Claude]

The downstream ModelingToolkit Julia 1.10 initialization failures have now been split precisely:

• 2 collector-invalidation errors are fixed in Fix collect_vars! after late invalidation on Julia 1.10 ModelingToolkit.jl#4852. The regression is bisected, covered on Julia 1.10/1.12, and the official Julia 1.10 InterfaceI group passes locally (1498 passed, 5 existing broken).
• the remaining 9 errors are the independent DelayDiffEq DEOptions resolver incompatibility tracked by Retroactively cap DelayDiffEq at OrdinaryDiffEqCore 4.8.0 JuliaRegistries/General#162781.

#4852 is a draft pending CI/review; this link is classification, not a claim that this PR's full matrix is green yet.