[ChrisRackauckas-Claude]

Drop unused NLsolve from [extras] / [targets].test / [compat]. Tests use NewtonRaphson and SimpleLimitedMemoryBroyden from NonlinearSolve, not NLsolve. NLsolve was only pulled so NonlinearSolveNLsolveExt would load.

Registered NonlinearSolve 4.x WeakCompat is NLsolve = "4.5.0-4" (["3 - 4.9"] and ["4.10 - 4"] in General). NLsolve 5 is live. With NLsolve kept as a test extra, Downgrade promotes extras into the merged resolve, so --min=@deps requires NLsolve 5 next to NonlinearSolve 4 and is unsatisfiable. SciML/NonlinearSolve.jl#1198 set NLsolve = "5" in source; that is not registered yet (latest NS is 4.28.0, still pinned to NLsolve 4.5-4).

This supersedes #241 (NLsolve = "4, 5"), which keeps extra major 4 so the min floor can still pick 4.5.1. NLsolve is unused here, so the extra should go rather than keep major 4.

file	change
Project.toml	remove NLsolve from [compat], [extras], [targets].test

NonlinearSolve stays at "4".

Verification

Local Julia 1.10.11. Resolver.jl --min=@deps --julia=1.10 on a merged extras project (same extras-to-deps promotion as julia-downgrade-compat):

Before (origin/main, NLsolve = "5" extra): Unsatisfiable

Unsatisfiable — 1 conflict:

Conflict 1: NLsolve, NonlinearSolve and OrdinaryDiffEqAdamsBashforthMoulton cannot all be satisfied.
  • you require NLsolve
  • you require NonlinearSolve
  • you require OrdinaryDiffEqAdamsBashforthMoulton
  • NonlinearSolve 4.0.0–4.25.0 works with NLsolve only at 4.5.0–4.5.1
  • your compat leaves NLsolve at ≥ 5.0.0
  Fix it by any one of:
    1. relax your compat on NLsolve
       → allows: NLsolve 4.5.1, NonlinearSolve 4.17.1,
         OrdinaryDiffEqAdamsBashforthMoulton 2.0.0
    2. drop requirement NLsolve
       → allows: NonlinearSolve 4.17.1, OrdinaryDiffEqAdamsBashforthMoulton
         2.0.0

After (NLsolve extra removed): EXIT 0. NLsolve is not in the resolved set. Direct floors include NonlinearSolve 4.17.1, OrdinaryDiffEq 7.0.0, OrdinaryDiffEqAdamsBashforthMoulton 2.0.0, ForwardDiff 1.0.1, Lux 1.16.0, SciMLSensitivity 7.105.0.

GROUP=Core Pkg.test() without NLsolve extra (test env Status has NonlinearSolve v4.28.0 and no NLsolve):

Test Summary: | Pass  Total     Time
Utils Tests   |   13     13  1m01.3s
Test Summary: | Pass  Total      Time
Layers Tests  | 1538   1538  24m19.3s
     Testing DeepEquilibriumNetworks tests passed

Started 2026-08-26T11:07:27-04:00, finished 2026-08-26T11:38:44-04:00.

Not verified

• GPU group (self-hosted CUDA)
• QA group
• docs build (no docstring / docs/ / public API change)
• Downstream

This PR should be ignored until reviewed by @ChrisRackauckas.

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