[P4] Rename .csproj files and project references (BREAKING)

[ChrisonSimtian]

Scope

```
source/Nuke.Common/Nuke.Common.csproj → Fallout.Common/Fallout.Common.csproj
source/Nuke.Build/... → Fallout.Build/...
source/Nuke.Components/... → Fallout.Components/...
... (and so on for every project)
```

Implications

• Solution file (`fallout.slnx`) project paths update.
• Every `<ProjectReference Include="...\Nuke.X.csproj" />` updates.
• Test projects (`*.Tests`) get the same treatment.
• `AssemblyInfo.cs` InternalsVisibleTo entries update.
• `` matches `` by default → packages auto-rename.
• nupkg files in `output/` switch names too.

Tooling

Best done in Rider with "Rename Project" — handles directory + file + reference updates atomically.

Sibling `*.Generated.cs`

Tool wrappers (`source/Nuke.Common/Tools//.json`) get regenerated under the new namespace. The `.json` file paths stay flat (`Tools//.json`) — the directory name `Tools` is part of the project layout, not the namespace.

Risk

Touches every PackageReference in downstream user projects. Coordinates with [P4] namespace rename — they typically land together.

Done when

• All projects renamed
• Solution loads in IDE without unresolved references
• `dotnet pack` produces `Fallout.*.nupkg` files
• No `Nuke.*` file paths remain

[ChrisonSimtian]

Rolled into #32. Per discussion on 2026-05-20, the namespace rename and the csproj/assembly rename are being done atomically in a single PR. Splitting them would have created an intermediate state where namespaces and assembly names disagree, which complicates InternalsVisibleTo, ProjectReference paths, and dogfooding.