[felipecm-br]

Summary

Adds ergonomic CLI configuration flags and improves configuration file discovery:

• --print-default-config: Prints the full default configuration YAML to stdout and exits (lazygit parity for users bootstrapping their configuration).
• -c / --config <path>: Enables loading a custom configuration file or preset (e.g. lazygitrs -c popup or lazygitrs -c ~/custom.yml).
• Tilde (~) Expansion: Expands leading ~ and ~/... using dirs::home_dir().
• .yaml and .yml Support: Discovers both config.yaml and config.yml across candidate config paths and presets.
• Informative Error Reporting: Produces a clear bail message if a specified configuration override or preset does not exist.
• Unit Tests: Full test suite covering CLI flags, tilde expansion, and config loading failure paths.

Verification

• cargo fmt verified.
• cargo test --bin lazygitrs (375 passed).