Investigate the inherited Nuke.* IDE add-on internals grants #547

Reminder to investigate — not scheduled.

Problem

AssemblyInfo.cs:22-28 still grants InternalsVisibleTo to five out-of-repo assemblies inherited from NUKE, all on the old namespace:

Nuke.VisualStudio, ReSharper.Nuke, ReSharper.Nuke.Rider,
Nuke.Remote.Functions, Nuke.Website.Functions

Two things bother me about this:

1. They're an unverifiable coupling. FT-2 (#451) made BuildManager.CancellationHandler a silent no-op outside an active run. Anything in that list subscribing before Execute now loses its handler quietly. Nothing in this repo can confirm whether that matters — the code lives elsewhere. Every future de-statification step (FT-4/5/6) has the same blind spot.
2. The namespace is wrong. These grants privilege Nuke.* internals access indefinitely, which cuts against the rebrand being otherwise done.

Outcome

Know what's actually on the other end of those grants, then decide: drop them, or replace them with first-party add-ons built clean.

Look into

• Are any of the five still maintained / still consuming Fallout internals? Which internals?
• Anything actually broken by the FT-2 no-op, or by the FT-1/FT-2 teardown?
• Which grants can just be deleted.
• First-party add-ons: ReSharper/Rider and Visual Studio, alongside the VS Code extension already underway (milestone chore: remove AppVeyor-era orphan code #22). Built fresh on Fallout.* — not ported.
• If we own the add-ons, does the internals surface need to be public/[Experimental] API instead of InternalsVisibleTo?

Related: #545, #546 (the untested seams that make #1 hard to reason about).