handoff — Fresh-session handoff doc skill

Compress a substantive arc into a single resumable doc the next agent loads cold.

Why this skill exists

Across the 7-day window 2026-05-18 → 2026-05-24, nine fresh-session handoff docs were drafted by hand. Six landed in docs/handoffs/ (Houston substrate completion, BRO-1208 streaming hang, Houston advanced-settings wave, Life-Houston H1 runner refactor, Stage 1 fresh-session, etc.) and three landed in docs/conversations/HANDOFF-* (substrate completion arc, BRO-1180 four pillars, Spec J real-Anthropic smoke). All shared the same shape — the recurrence met rule-of-three (P16) ~3× over.