Turn a one-off Python script into a proper CLI tool

Convert the script described below into a real command-line tool — not a script with sys.argv indexing, and not one that still has hardcoded values a user has to edit before running it.

CURRENT SCRIPT
A script that reads a folder path and a threshold hardcoded at the top, then deletes log files older than the threshold.

FRAMEWORK
Use Typer. If it's Typer, define arguments as type-hinted function parameters — that's Typer's actual mechanism — rather than manually building a parser. If it's Click, use the @click.command() and @click.option/@click.argument decorators. If it's argparse, use argparse.ArgumentParser with explicit type=, required=, and help= on every argument.

COMMANDS NEEDED
single command: clean, with options for folder, days-old threshold, and file extension filter

REQUIREMENTS
1. Every option has a help string a stranger could act on without reading the source.
2. Every option with a sensible default gets one; every option that doesn't must be required and say so, rather than silently defaulting to None and failing three lines later with an unrelated error.
3. Validate inputs at the CLI boundary (file exists, path is a directory not a file, number is in range) and exit with a clear message and a non-zero exit code — never a raw traceback as the user-facing output.
4. Use meaningful exit codes: 0 for success, and distinct non-zero codes for distinct failure classes if there's more than one, documented in a comment.
5. If the tool does anything destructive (deletes files, overwrites data), add a --dry-run flag and default destructive behavior to off unless --yes or --force is passed.

OUTPUT FORMAT
1. The CLI entry point code.
2. The exact pyproject.toml [project.scripts] entry needed to install it as a real command.
3. Three example invocations: one happy path, one that fails validation, one using --dry-run if applicable.