Enhance file validation in sidekick command

Modified the 'sidekick' command in 'cli.py' to include file validation. Now, the 'files' argument checks if the provided path exists and is readable. This should prevent errors caused by invalid file paths and enhance overall robustness of the command. 📁🔍

aicodebot/cli.py

@@ -445,7 +445,7 @@ def review(commit, verbose, output_format, response_token_size, files):
 @click.option("-n", "--no-files", is_flag=True, help="Don't automatically load any files for context")
 @click.option("-m", "--max-file-tokens", type=int, default=10_000, help="Don't load files larger than this")
 @click.option("-v", "--verbose", count=True)
-@click.argument("files", nargs=-1)
+@click.argument("files", nargs=-1, type=click.Path(exists=True, readable=True))
 def sidekick(request, verbose, no_files, max_file_tokens, files):  # noqa: PLR0915
     """
     Coding help from your AI sidekick