Function validate_edit_target 

pub fn validate_edit_target(
    workspace_root: &Path,
    thread_id: &str,
    requested_path: &Path,
    resolved_path: &Path,
    previous_bytes: Option<u64>,
    new_bytes: u64,
) -> Result<()>

Validate one FileWriteOrEdit target. Non-temporary project files keep their existing behavior; only legacy Winx root artifacts and .winx/tmp receive this additional governance.