Rebrand the global-tool startup banner from NUKE to Fallout

[ChrisonSimtian]

What

The CLI's startup banner still printed NUKE Global Tool 🌐:

src/Fallout.Cli/Program.cs:42
    Host.Information($"NUKE Global Tool 🌐 {typeof(Program).Assembly.GetInformationalText()}");

Changed to Fallout Global Tool 🌐.

Why

A leftover the command/package rebrand missed — #66 renamed the command (nuke→fallout) and #371 publishes the package as Fallout.GlobalTools, but this runtime banner literal was never updated. It's the first line a user sees on every dotnet fallout invocation.

Note for the in-flight CLI refactors

The same literal is currently carried forward (unchanged) by the open refactor PRs:

• Collapse Program to a thin entry point; extract residual helpers into services (#392) #404 (cli-cmd-collapse) moves it into CliConventions.cs as ToolBanner
• Convert the :navigation cluster to command types (#392) #403 (cli-cmd-navigation) leaves it in Program.cs

Whichever lands first, the string should end up as Fallout Global Tool 🌐. Trivial conflict either way — flagging so it isn't silently re-introduced.