Function detect_changed_plugins 

pub fn detect_changed_plugins(
    config: &MarketplaceConfig,
) -> Result<Vec<String>, SoukError>

Detect which plugins have changes staged for commit.

Runs git diff --cached --name-only and matches paths against the configured pluginRoot. Returns a deduplicated, sorted list of plugin directory names that have at least one staged file.

Errors

Returns SoukError::Other if the git command fails to execute or exits with a non-zero status.