Swap published columns for 24 entries from random.md

Retract the seven published columns into drafts/ and promote the 24 per-date
entries split out of Notes/random.md. Bodies are verbatim; titles, subjects
and slugs are new.

Make publication a matter of location. Notes/Notes.11tydata.js gives anything
under Notes/ permalink: false unless tagged `column`; drafts/drafts.11tydata.js
renders drafts at their real permalink under `yarn dev` and excludes them from
collections entirely in a build, so no template can surface one. Publishing is
now `git mv drafts/<file> columns/`, and moving it back retracts it.

Untagged notes were previously rendered into _site/ and deployed — including
Notes/random.md, which was live at /Notes/random/.

.eleventy.js

@@ -75,11 +75,28 @@ module.exports = function (eleventyConfig) {
   eleventyConfig.addShortcode("image", imageShortcode);
   eleventyConfig.addShortcode("heroImage", heroImageShortcode);
 
-  // A "column" is anything tagged `column`, wherever it lives on disk
-  // (some columns are authored under Notes/). Newest first.
+  // A "column" is anything tagged `column`, wherever it lives on disk.
+  // Newest first.
+  //
+  // Drafts carry the `column` tag too — their front matter is complete so that
+  // promoting one is a plain `git mv` — so they must be filtered out here by
+  // the `draft` flag that drafts/drafts.11tydata.js sets. This collection
+  // feeds the homepage and the sidebar archive; a draft in it would be listed
+  // sitewide.
   eleventyConfig.addCollection("columns", function (collectionApi) {
     return collectionApi
       .getFilteredByTag("column")
+      .filter((item) => !item.data.draft)
+      .sort((a, b) => b.date - a.date);
+  });
+
+  // Drafts, newest first, for the /drafts/ index. The collection is populated
+  // in both run modes, but the only page that reads it lives under drafts/ and
+  // so is itself unwritten during `yarn build`.
+  eleventyConfig.addCollection("drafts", function (collectionApi) {
+    return collectionApi
+      .getAll()
+      .filter((item) => item.data.draft)
       .sort((a, b) => b.date - a.date);
   });
 
@@ -89,6 +106,7 @@ module.exports = function (eleventyConfig) {
     const reserved = new Set(["all", "column"]);
     const subjects = new Set();
     for (const item of collectionApi.getFilteredByTag("column")) {
+      if (item.data.draft) continue;
       for (const tag of item.data.tags || []) {
         if (!reserved.has(tag)) subjects.add(tag);
       }