Function write_chart_to_disk 

pub fn write_chart_to_disk(
    path: &Path,
    bytes: &[u8],
    overwrite: bool,
) -> Result<u64, McpError>

Write chart bytes to path, creating the parent directory if needed and honoring the overwrite flag.

Errors:

• PermissionDenied if path exists and overwrite=false (matches export’s pre-flight check).
• InternalError wrapping the underlying std::io::Error for mkdir or write failures.

Returns the number of bytes written.

Errors

• Returns ErrorCode::PermissionDenied if path exists and overwrite is false.
• Returns ErrorCode::InternalError wrapping the underlying std::io::Error for create_dir_all or write failures.