Function validate_files_readable 

pub fn validate_files_readable(
    files: &[PathBuf],
) -> AnalysisValidation<Vec<FileContent>>

Validate that files can be read, accumulating ALL read errors.

Returns a validation containing either all successfully read files or ALL errors encountered during reading.

Example

let files = vec![
    PathBuf::from("src/good.rs"),
    PathBuf::from("/nonexistent/path"),
    PathBuf::from("src/also_good.rs"),
];

let result = validate_files_readable(&files);
// If /nonexistent/path doesn't exist, failure contains that error
// but also includes any other missing files