// workflow step: validate — check the post has a title + enough body.
// Output { ok, word_count, issues } → gates the rest of the DAG via `when`.
let b = ctx.request.body;
let post = docs::collection("posts").get(b.post_id);
if post == () {
    return #{ ok: false, issues: ["post not found"], word_count: 0 };
}
let d = post.data;
let issues = [];
if d.title == () || d.title == "" { issues.push("missing title"); }
let body = if d.body_md == () { "" } else { d.body_md };
let words = if body == "" { 0 } else { body.split(" ").len() };
if words < 3 { issues.push("body too short"); }
#{ ok: issues.len() == 0, word_count: words, issues: issues }