Add environment variable support for CLI flags and refactor utilities module

Summary

This PR adds environment variable support for the --report and --command-borders CLI flags with precedence order defaults → env_file → os.environ → CLI args. It also moves util.py and boolean.py into a src/molecule/utils/ package.

User-Facing Changes

Environment Variable Support

New environment variables:

• MOLECULE_REPORT=true - equivalent to --report
• MOLECULE_COMMAND_BORDERS=false - equivalent to --command-borders

Environment variables are applied only when CLI arguments are not explicitly provided:

export MOLECULE_REPORT=true
molecule test                    # Uses env var

MOLECULE_REPORT=true molecule test --no-report  # CLI overrides env var

echo "MOLECULE_REPORT: true" > .env.yml
molecule test --env-file .env.yml               # Reads from env file

Supported boolean formats: true/false, yes/no, on/off, 1/0 (case-insensitive).

Implementation Details

Design Decision: New Pattern vs Existing

Molecule already supports some environment variables (MOLECULE_DEBUG, MOLECULE_VERBOSITY) but uses a pattern that has limitations:

# Existing pattern
MOLECULE_DEBUG: bool = boolean(os.environ.get("MOLECULE_DEBUG", "False"))
@click.option("--debug/--no-debug", default=MOLECULE_DEBUG, ...)

Issues with existing pattern:

• No CLI override detection (env vars become Click defaults)
• Module-level evaluation (no runtime flexibility)
• No env file support (only reads os.environ)
• Requires individual changes per environment variable

New pattern:

def _apply_env_overrides(self) -> None:
    merged_env = util.merge_dicts(os.environ, self.env)
    merged_env = set_env_from_file(merged_env, self.env_file)
    
    for env_var, config in ENV_VAR_CONFIG_MAPPING.items():
        if ctx.get_parameter_source(config_attr) == click.core.ParameterSource.COMMANDLINE:
            continue  # CLI takes precedence
        # Apply env var...

Improvements:

• Proper CLI precedence via Click's parameter source detection
• Full env file integration using existing set_env_from_file()
• Runtime evaluation during config initialization
• Extensible mapping-based configuration
• Type-safe conversion

Environment Variable Processing

1. Builds merged environment from os.environ, config.env, and env files
2. Uses ctx.get_parameter_source() to detect explicit CLI arguments
3. Applies type conversion based on ENV_VAR_CONFIG_MAPPING
4. Runs before _apply_cli_overrides() to maintain precedence

Configuration mapping:

class EnvVarConfig(TypedDict):
    attr: Literal["report", "command_borders"]
    type: type

ENV_VAR_CONFIG_MAPPING: dict[str, EnvVarConfig] = {
    "MOLECULE_REPORT": {"attr": "report", "type": bool},
    "MOLECULE_COMMAND_BORDERS": {"attr": "command_borders", "type": bool},
}

Circular Import Resolution

Initial circular dependency: ansi_output.py → util.py → console.py → ansi_output.py

Resolution:

1. Moved to_bool() to dedicated boolean.py module
2. Organized both files into src/molecule/utils/ package
3. Updated all imports to use explicit paths: from molecule.utils.boolean import to_bool

Module Refactoring

• src/molecule/util.py → src/molecule/utils/util.py
• src/molecule/boolean.py → src/molecule/utils/boolean.py
• Added minimal src/molecule/utils/__init__.py

Testing

Added comprehensive test coverage for environment variable application, CLI precedence validation, and type conversion. All existing tests continue to pass.

Future Migration Path

Other environment variables (MOLECULE_DEBUG, MOLECULE_VERBOSITY, MOLECULE_PARALLEL) could be migrated to this new framework to gain:

• Consistent CLI precedence handling
• Env file support
• Extensible configuration
• Type-safe conversion

This would require updating their Click option definitions and adding entries to ENV_VAR_CONFIG_MAPPING.