QA: Aqua piracies known-broken (intentional ArrayInterfaceCore.can_setindex piracy)

[ChrisRackauckas-Claude]

Tracking issue for the aqua_broken = (:piracies,) placeholder in test/qa.jl (run_qa v1.6 form).

Aqua.Piracy.hunt(ComplementaritySolve) reports 2 methods (both intentional, in the documented ### Type Piracy ### block of src/ComplementaritySolve.jl):

- can_setindex(::Type{<:FillArrays.AbstractFill}) @ ComplementaritySolve src/ComplementaritySolve.jl:50
- can_setindex(::Zygote.OneElement)               @ ComplementaritySolve src/ComplementaritySolve.jl:51

These override ArrayInterfaceCore.can_setindex (function owned by ArrayInterfaceCore) for FillArrays.AbstractFill and Zygote.OneElement (types owned by FillArrays/Zygote) so the solver paths treat those lazy arrays as immutable. This is the same suppression the pre-1.6 test/aqua.jl carried as piracies = (; broken = true).

The conversion preserves it as a tracked @test_broken via aqua_broken = (:piracies,). Close this issue and drop :piracies from aqua_broken once the piracy is resolved (e.g. by upstreaming the can_setindex definitions to ArrayInterfaceCore, or moving them behind an Aqua treat_as_own/package-extension that no longer trips the piracy hunt).

[ChrisRackauckas-Claude]

Opened two PRs to resolve this:

• Upstream: Add FillArrays extension for can_setindex JuliaArrays/ArrayInterface.jl#493 — adds a FillArrays extension defining can_setindex(::Type{<:AbstractFill}) = false and can_setindex(::Type{<:OneElement}) = false, the proper home for this behavior (can_setindex is owned by ArrayInterface).
• Here: Remove ArrayInterfaceCore can_setindex type piracy (resolves #68) #70 — removes the local piracy and re-enables the Aqua piracy check.

Notes from investigating:

• The pirated methods were defined on the deprecated ArrayInterfaceCore.can_setindex, while the current solver stack dispatches on ArrayInterface.can_setindex — so they were effectively dead.
• Zygote.OneElement is no longer constructed by current Zygote; getindex gradients flow through ChainRules.OneElement, which ArrayInterface already handles. Only the FillArrays side needed upstreaming.

#70 is independently correct/mergeable now (registry-ArrayInterface QA passes with the piracy check on); ArrayInterface.jl#493 provides the immutability behavior going forward.