Function load_token_file 

pub fn load_token_file(path: &Path) -> Result<TokenFile, TokenError>

Load a multi-theme token file.

Expects either:

• { "themes": { "light": { ... }, "dark": { ... } } } (multi-theme)
• { "token-name": "value", ... } (flat — treated as a single "default" theme)

Errors

Returns TokenError::Io if the file cannot be read, TokenError::InvalidJson if parsing fails, or TokenError::Schema if the structure is invalid.