Release v1.2.0 — webapp visualizer + repo health
feat(webapp): full rewrite — light theme, embedded sparklines, true marginals
feat(webapp): K selector, auto-detect artifacts dir, factor source indicator
fix(bp): _message_delta falls back to moment comparison on K mismatch
fix(webapp): sparkline clip-path, shared x-domain, clamped xScale
fix(webapp): belief updates in animation on('end') callback
fix(webapp): sanitize inf/nan → null not 0.0
fix(webapp): default damping 0.3, max_iter 40
fix(cli): ComplexityResult/Sequence type annotations
feat: __version__ exported from gmbp
chore: pytest-cov in dev deps, CI coverage + mypy jobs, .gitignore