Add support for -c/--command option to execute commands and exit

[DiegoDAF]

Summary

This PR adds support for the -c/--command option to pgcli, implementing psql-compatible behavior for executing SQL commands or internal commands from the command line.

This is PR #1530, cleaned.

Features

• Single command execution: pgcli -c "SELECT 1"
• Multiple commands: pgcli -c "SELECT 1" -c "SELECT 2"
• Long form support: pgcli --command "SELECT 1"
• Mixed usage: pgcli -c "cmd1" --command "cmd2"
• Commands are executed sequentially
• Pager is automatically disabled in command mode
• Proper error handling and exit codes

Implementation Details

• Added new click option -c/--command that accepts multiple values
• Modified run_cli() to check for command mode and execute commands before entering interactive mode
• Updated echo_via_pager() to disable pager when in command mode
• Commands are executed using the existing handle_watch_command() method

Testing

Comprehensive BDD tests included covering:

• Single command with -c flag
• Single command with --command flag
• Multiple statements in one command
• Multiple -c options
• Mixed -c and --command options
• Error handling

Compatibility

This implementation follows psql's behavior and maintains backward compatibility with existing functionality.

Made with ❤️ and 🤖 Claude Code