Adds kamal alias: list existing aliases

[supercobra]

kamal alias lists existing aliases from deploy.[target].yml files.

Example:

$ kamal alias -d production                                                                   
console                        app exec --interactive --reuse "bundle exec rails console"     
shell                          app exec --interactive --reuse "bash"                          
logs                           app logs -f                                                    
dbc                            app exec --interactive --reuse "bundle exec rails dbconsole"  

[Copilot]

Pull Request Overview

This PR adds a new kamal alias command that displays all available aliases from the configuration files. The command shows aliases in a formatted table with names left-aligned in a 30-character column followed by their corresponding commands.

• Adds kamal alias command to list configured aliases
• Provides formatted output showing alias names and their commands
• Handles cases where no aliases are configured

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
lib/kamal/cli/main.rb	Implements the new alias command with formatting logic
test/cli/alias_test.rb	Adds comprehensive test coverage for the alias command functionality

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[Copilot]

The magic number 30 for column width is hardcoded. Consider extracting this to a constant like ALIAS_NAME_COLUMN_WIDTH = 30 to improve maintainability and make the formatting intention clearer.