Bring PLAN.md and TASKS.md up to date

PLAN.md: the self-review report replaces the old report section, Heavy is shown as coming soon, what each part does, priorities and what was done on 4 Oct, the stricter guard and spoken skip, the checklist (repo public, credits, licences, demo link) and the open decisions. TASKS.md: the README is done, and better speech recognition is noted as a P2 in two steps.