Decide: re-home Nuke.* transition shims off GitHub Packages to drop the PAT requirement

## Context

GitHub Packages (NuGet) **requires a token even for public packages** — there's no anonymous access (unlike ghcr). The `Nuke.*` transition shims live on GitHub Packages **only**, because the `Nuke.*` IDs are owned by the original NUKE maintainer on nuget.org (#47). So a NUKE consumer migrating via the shims must add a `read:packages` PAT to their `nuget.config` — the most consumer-facing auth friction we have.

## Decision (deferred — not worth it yet)

- **Option A (current):** accept it; document the one-line `nuget.config` + PAT step. Fine for a technical transition audience.
- **Option B (maybe later):** re-home the shims under an **org-owned ID on nuget.org** (e.g. `Fallout.Shims.*`) so they're anonymous/PAT-free — at the cost of the drop-in `Nuke.*` name (consumers change a using/package ref instead of zero-touch).
- Option C (proxy a token in front of the GH feed) — rejected, hacky.

Going with **A** for now. Re-evaluate B if shim-PAT friction shows up in real migration feedback.

Related: #47. Surfaced during the org/package-ownership migration.