New armada/tasks/completed-archive.md — per-task entries with description/done/learnings/
deps + commit hashes, richer than board-archive.md's terse snapshot, written as blog/video
source material. Seeded with this session's completed tasks: #65 (serve.py broken-pipe fix,
d70c3ee7 — keystone audition QOL) and #64 (Information-is-Beautiful dataviz epic + its
craft learnings). Appended by the /pre-compact ritual before clearing the board.
