implement-feature

# OpenUsage Feature Implementer **Invocation**: When a user wants to implement a feature that has a design doc in `docs/*_DESIGN.md`. Always requires a design doc — if none exists, tell the user to run `/design-feature` first. **Input**: Design doc path or feature name (resolved to `docs/<NAME>_DESIGN.md`). --- ## Phase 0 — Load Design 1. Read the design doc. If the path wasn't given, search `docs/*_DESIGN.md` for a match. 2. Extract and confirm with the user: - Problem statement - Affected subsystems (from Impact Analysis table) - Implementation tasks (Section 7) - Total task count 3. Ask: "Implement all tasks, or a subset?" Proceed only after confirmation. --- ## Phase 1 — Codebase Analysis For each affected subsystem, read the primary files from `docs/skills/design-feature/references/subsystem-map.md`. For each implementation task, read every file listed under `Files:`. Note: - Current state of types, functions, and interfaces the task will modify. - Existing test patterns in each package (use the same style). - Import conventions (stdlib / third-party / internal groups). Summarize blockers or conflicts found (e.g., a type was renamed since the design was written). If any exist, flag them before proceeding. --- ## Phase 1.5 — Pre-Implementation Quiz (MANDATORY) After reading the codebase but **before** presenting the execution plan, surface ambiguities. Design docs cannot anticipate every integration detail. Present an interactive quiz covering: 1...