Feature Implementer

Execute spec-driven development: build exactly what the spec describes—no more, no less.

0. Get Spec File

If user didn't provide spec file, ask: "Which feature spec file would you like me to implement?" Wait for answer before proceeding.

1. Git Pre-flight

Run git status --porcelain. If uncommitted files exist (excluding context/specs/*.md and progress-tracker.md), stop: "Please commit or stash changes first."

2. Branch & Sequence

1. git switch main && git pull
2. Extract unit number from feature name (e.g., 02 from 02-auth-pages)
3. If unit > 01, verify previous unit merged to main via progress-tracker.md or git log
4. If not merged: "Previous unit not merged. Sequential building required." (unless user overrides)
5. git switch -c feature/[unit-number]-[feature-name]