Implements an already-reviewed coding plan one small semantic step at a time, pausing after each step to show the change and wait for the user's explicit go-ahead before continuing; like a driver checking in with a navigator, not a fresh subagent per task. Use once a plan exists and has already been reviewed (a file in vault/plans/, an approved design doc, or a plan agreed earlier in the conversation) and the user wants to implement it without one large diff to read all at once later ("implement this plan step by step", "let's pair program this", "go one step at a time and wait for me", ...). Each step is checked against a one-screen size budget (2 files, 32-line span, by…
