Feature/provider command

[aaron-riact]

No description provided.

[Copilot]

Pull Request Overview

This PR introduces client configuration management commands to enable users to interact with provider configurations through a CLI interface.

• Adds new client command with subcommands for listing providers and initializing configuration
• Refactors client configuration handling into reusable utility functions
• Adds terminal detection for improved output formatting

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
main.go	Adds client command structure with provider list and init-config subcommands
go.mod	Adds golang.org/x/term dependency for terminal detection
flake.nix	Updates vendor hash for new dependencies
commands/login.go	Refactors to use new client config utility functions
commands/config/client_config.go	Adds utility functions for config path resolution and file operations

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