Add `make board` and docs/board.md so the Board's rebuild-and-redeploy flow
is a documented step, not tribal knowledge. Covers why the county data is
inlined (self-contained Artifact / CSP), that build_viz.py injects it into
board.html, and that a live Artifact must be REPUBLISHED (editing the repo
file doesn't update a deployed Artifact). README links it in both the make
list and the docs index.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Fabio