ai-dev-tasks: PRD to Task List to One-Subtask-at-a-Time AI Workflow

Uses two Markdown templates (create-prd.md and generate-tasks.md) to turn 'dumping a pile of requirements on AI' into a controlled process: first generate a PRD, break it into a checkable task list, then complete one subtask at a time — pausing after each for your go-ahead before continuing.