Function pause_spec 

pub fn pause_spec(
    spec: &mut Spec,
    spec_path: &Path,
    options: PauseOptions,
) -> Result<bool>

Pause a running work process for a spec.

This is the canonical pause logic:

• Checks for PID file and running process
• Stops the process if running (respecting force flag)
• Updates spec status from in_progress to paused
• Cleans up PID file

Returns Ok(true) if a process was stopped, Ok(false) otherwise.