Refactor compose file flag into shared OptionGroup for up, down, and build.

[Copilot]

The compose file flag handling was duplicated across the two compose commands that accept -f/--file. This change centralizes that option in a shared argument group and wires both commands to consume it consistently.

• Shared CLI option model

  • Added ComposeFileOptions as a reusable ParsableArguments type for -f/--file.
  • Keeps compose-file option definition in one place for both commands.

• Command integration

  • Updated ComposeUp to use @OptionGroup var composeFileOptions.
  • Updated ComposeDown to use @OptionGroup var composeFileOptions.
  • Switched internal compose-file resolution paths to read from the shared option group.

• Parsing coverage

  • Added static parsing tests to assert ComposeUp and ComposeDown both accept -f my-compose.yaml through the shared group.

public struct ComposeFileOptions: ParsableArguments, Sendable {
    @Option(name: [.customShort("f"), .customLong("file")], help: "The path to your Docker Compose file")
    public var composeFilename: String?
}

@OptionGroup
var composeFileOptions: ComposeFileOptions

[Mcrich23]

These tests are kinda useless. However, check if calling "-f", "up" on the main entry point command is valid.

[Mcrich23]

Double check the change on this variable name

[Mcrich23]

This looks decent @copilot. Please look at the comments I left.