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/.

drafts/_template.md

@@ -0,0 +1,17 @@
+---
+title: <Title Case>
+date: <YYYY-MM-DD>
+layout: column.njk
+tags: [column, <computing | philosophy | society | writing>]
+permalink: /columns/<year>/<slug>/
+---
+
+Open in the middle of the thought. No headline restated, no throat-clearing —
+column.njk renders `title` as the h1 already, and the shortest columns are a
+single unbroken paragraph that starts where the idea starts and stops when it
+runs out.
+
+Copy this to drafts/<YYYY-MM-DD>-<slug>.md and fill the front matter in. It
+renders at its real permalink on the dev server and nowhere else. Publishing is
+`git mv drafts/<file> columns/` — the front matter is already complete, so
+leaving this directory is the whole act, and moving it back retracts it.