Two release modes — single vs multi, config-selected

Monorepos need independent per-package versions and tags (api-v1.0.0, shared-v0.3.1); single-package repos need one repo-wide version. We considered making every repo implicitly multi-package (a non-monorepo just has one Package, prefix .) to avoid a mode switch, but that forces monorepo concepts (per-package tag patterns, N draft releases) onto the common single-repo case where they add nothing. Instead .draftsman.yml declares mode: single | multi explicitly: single keeps one Draft Release with a repo-wide version and uses Packages only to section entries within it; multi maintains one Draft Release per Package with independent versions and tags.

Consequences

Switching a repo from single to multi later re-partitions version history per package — existing single tags don't map cleanly onto per-package tag sequences. This is a decision best made early.