Audit triggered while debugging the v0.2.0 release surfaced drift in
the maintainer docs vs current code: dead curated_defaults.json
references (file replaced by starter_preset.json in PR #72), the
v1_0_1 fork example (removed in v0.1.5), and a "tooling we don't have
yet" entry that's now covered by tools/preflight_release.py. Adds a
new conventions.md for cross-cutting rules — currently the
Mermaid-for-diagrams convention.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
