Convert to System.CommandLine

[geofflamrock]

Converts from Spectre.Console.Cli to System.CommandLine@2.0.0-beta5 now that it has a path to a stable version, paving the way for enabling AOT.

A few changes with this:

• The way command help is displayed (no more colour or groups) but this is ok for the moment.
• There was some inconsistency in the way that branches were referenced in some commands, these have been consolidated to be --branch.

Fixes #277

Part of a series of PRs that are adding support for AOT:

• Convert to System.CommandLine #276
• Use source generator for Json serialization #285
• Update to Spectre.Console.Cli 0.50.0 #280
• Replaces Octopus.Shellfish with directly using Process #284
• Update to Humanizer.Core v3 beta #286
• Enable publishing with Native AOT #287
• Enable trimming during publish #288
• Remove Humanizer #290
• Update readme to reflect new command options #297
• Remove --working-directory alias #298

[Copilot]

Pull Request Overview

This PR converts the command infrastructure from Spectre.Console.Cli to System.CommandLine in order to support AOT and simplify the CLI setup.

• Removed legacy Spectre.Console.Cli-based settings and registrations.
• Introduced System.CommandLine-based commands and common options across commands.
• Updated package references and refactored command handler invocations accordingly.

Reviewed Changes

Copilot reviewed 32 out of 32 changed files in this pull request and generated 1 comment.

File	Description
src/Stack/Stack.csproj	Updated package references to replace Spectre.Console.Cli with System.CommandLine and Spectre.Console.
src/Stack/Program.cs	Replaced CommandApp configuration with a StackRootCommand setup using System.CommandLine.
src/Stack/Infrastructure/Commands/*	Converted all commands from the old CLI pattern to the new System.CommandLine API.
Other command files	Updated command option definitions and handler invocations to use ParseResult from System.CommandLine.

Comments suppressed due to low confidence (1)

src/Stack/Commands/Stack/NewStackCommand.cs:28

• [nitpick] The option identifier 'StackName' might be confusing since this command creates a new stack; consider renaming it to 'Name' to remain consistent with its usage.

    static readonly Option<string?> StackName = new("--name", "-n")

[Copilot]

[nitpick] Consider renaming the 'json' parameter to 'isJsonOutput' or a similar more descriptive name to clearly indicate it is a flag controlling the output format.