fix: properly flattening CLI arguments from the common structure

[nicolasnoble]

This makes the CLI arguments work properly in the client CLI, like they do on the server.

[Copilot]

Pull request overview

This PR refactors the CLI argument handling to eliminate duplication by introducing a shared ClientArgs structure that is flattened into the CLI-specific argument structure. This creates a single source of truth for client configuration arguments.

Key Changes

• Introduced ClientArgs as a shared structure for common client arguments (endpoint, timeout, cache settings)
• Used #[command(flatten)] to embed ClientArgs into the CLI's Cli structure
• Removed duplicate argument definitions from the CLI binary
• Added comprehensive documentation explaining the architecture and how to add new arguments
• Reorganized ClientConfig::load() with clear sections for applying CLI argument overrides
• Added extensive test coverage for argument parsing and configuration loading

Reviewed changes

Copilot reviewed 1 out of 3 changed files in this pull request and generated no comments.

File	Description
modelexpress_common/src/client_config.rs	Added Clone derive to ClientArgs, removed -v short flag from log_level to avoid conflict with CLI's verbose flag, added extensive documentation about the argument architecture, reorganized ClientConfig::load() with clear sections, and added comprehensive tests for argument parsing
modelexpress_client/src/bin/modules/args.rs	Refactored to flatten ClientArgs into Cli struct, removed duplicate argument definitions (endpoint, timeout, cache_path, quiet), added extensive documentation, and added PartialEq derive to OutputFormat for test assertions
modelexpress_client/src/bin/cli.rs	Simplified main function by directly using flattened client_args, removed manual construction of ClientArgs, updated all references to use cli.client_args.*, added module-level documentation explaining the argument architecture, and added comprehensive integration tests

[nv-hwoo]

Thanks for the fixes. Do we know why some checks are failing?

[AndyDai-nv]

@nv-hwoo I suspect one of the failures is some access issue, token expiration or sth... Created one ticket in the backlog

[nv-hwoo]

LGTM

[nv-hwoo]

@nicolasnoble looks like there's a clippy failure on the "Test Suite" check (thanks @AndyDai-nv for pointing out).