Switching to a two-branch workflow: contributors open PRs against `dev`,
and `main` is fast-forwarded to a tested `dev` commit at each release.
This separates "things land in staging" (can move fast) from "things
ship to users" (slow, tested in a browser by the maintainer first).
CONTRIBUTING: add a Branch model section explaining the split + how to
retarget a PR.
PR template: add an explicit "this PR targets dev" checkbox at the top
so it's the first thing a contributor confirms.
End-users cloning the repo will now land on `dev` by default; they can
`git checkout main` if they want the curated branch.
041c03bf11