[P6] Update CI generation templates and tool-wrapper JSON references

[ChrisonSimtian]

Scope

The auto-generated CI configurations (GitHub Actions, etc.) include a header comment:

```

- To trigger manual generation invoke:

nuke --generate-configuration GitHubActions_xxx --host GitHubActions

```

After [P6.1] rename, that becomes `fallout --generate-configuration ...`.

Also: the tool-wrapper JSON spec files (`source/Fallout.Common/Tools//.json`) contain links pointing at `https://github.com/nuke-build/nuke/blob/master/source/Nuke.Common/Tools//.json` for the source-file provider. These resolve via:

```csharp
sourceFileProvider: x => GitRepository.SetBranch(MainBranch).GetGitHubBrowseUrl(x.SpecificationFile)
```

That auto-derives from `GitRepository`, so it'll naturally update to `ChrisonSimtian/fallout` after the repo rename. But the upstream-historical URLs baked into existing released specs are static. Comment in JSON specs may also reference URLs. Audit + update.

Done when

• Generated YAML/Kotlin headers say `fallout --generate-configuration` not `nuke`
• Tool spec JSON files have no stale `nuke-build/nuke` references
• Regenerate every tool wrapper via `./build.ps1 GenerateTools` and verify