aih-milestonelisted

## Task Manage a milestone end-to-end: gathering (default), plan-promotion (`--plan`), or direct execution (`--execute` or start-intent). Execution pipeline lives in `annexes/execution.md`; plan-promotion in `annexes/promotion.md`. $ARGUMENTS ## Flags - `--execute` — skip gathering, go straight to execution (backward-compat one-shot behavior). - `--plan [slug]` — seed a milestone draft from an existing `PLAN.md`, then enter gathering. See `annexes/promotion.md`. - `--from-brainstorm [slug]` — seed CONTEXT.md from `.aihaus/brainstorm/[slug]/BRIEF.md` (see Step 0). - `--no-split` — bypass the force-split decision gate (see `annexes/promotion.md` Step P1.6). ## Step 0 — `--from-brainstorm <slug>` intake (conditional) If `$ARGUMENTS` contains `--from-brainstorm <slug>`, run before Step 1. Otherwise skip. 1. Resolve `.aihaus/brainstorm/<slug>/BRIEF.md`. Emit the exact error string and abort if: - Slug dir does not exist → `No brainstorm found at <slug>. Run /aih-brainstorm first or check the slug.` - BRIEF.md missing → `Brainstorm at <slug> has no BRIEF.md — run was not completed. Re-run /aih-brainstorm <slug>.` - BRIEF.md missing any required H2 header below → `BRIEF.md at <slug> is missing section(s): <list>. Cannot seed plan.` (string identical to `/aih-plan` — do not swap "plan" for "milestone"; `<list>` = comma-separated missing headers). Required H2 headers: `Problem Statement`, `Perspectives Summary`, `Key Disagreements`, `Challenges`, `Research Evidence`,