implementation-planninglisted

# Implementation Planning ## Purpose Convert a drafted spec into the artifacts an AI Developer session needs to execute: a letter-decision matrix, a numbered task chain, a verification-gate contract, and a saved handoff prompt. ## When to invoke - Active phase is `Plan` or `Decisions` (per FLOW_RULES state announcement) - A spec exists at `docs/specs/<slug>/spec.md` with status `DRAFT` and clarify questions resolved - Operator says "plan this" / "draft decisions" / "let's break this into tasks" ## Do not invoke when - Spec status is still `DRAFT` with unresolved clarify questions (re-invoke `requirements-specification` instead) - Spec is `LOCKED` and decisions/tasks already exist (use `code-review` or `validation-and-qa` instead) - Operator wants to skip planning and start coding directly — STOP. FR-02 (plan before edit) requires written tasks. ## Documentation tier gate (FR-23) Before drafting any planning artifact, apply the tier from `flow-skills/documentation-budget/SKILL.md` (don't duplicate it). Create each artifact ONLY when its trigger holds: | Artifact | Create only when | |---|---| | `decisions.md` | a **real** decision exists — alternatives with rejection reasons or a locked tradeoff to preserve. No real decision → omit the file (do not write single-option "decisions"). | | `tasks.md` | Tier 3/4 (multi-file Full-lane work). Reference ACs by pointer (`spec.md` AC1..ACn); do not reprint them. | | `verification-gate.md` | Full lane **or** `policies/required-a