Function detect_workflow 

pub fn detect_workflow(repo_dir: &Path) -> Workflow

Auto-detect verification workflow from project files in the repo. Scans the repo root AND immediate subdirectories for ALL known language markers and creates steps for each. When a marker is found in a subdirectory, step.work_dir is set so the scheduler runs the command in the correct directory. Returns a no-stage workflow (auto-approve) if no known project type found.