refactor: rename content types to semantic taxonomy

- vault → notes (PKM-exported content)
- posts → articles (short-form, no TOC)
- papers → essays (long-form, with TOC)
- type: post → type: article (posts are just short articles)
- layouts/paper → layouts/essay
- 08a-paper.css → 08a-essay.css
- CSS: fix redundant li resets, remove role="main" from article,
  replace <small> prev/next labels, add console layout
- Update hugo.toml menus, internal URLs, front matter throughout
- Add docs/context.md, docs/css-refactor-plan.md

content/notes/tasks.md

@@ -0,0 +1,38 @@
+---
+title: "Tasks"
+description: "Render task lists with semantic state: done, wip, blocked, todo."
+section: notes
+prev-url: ""
+prev-title: ""
+next-url: "wikilinks/"
+next-title: "Wikilinks"
+type: notes
+date: 2026-04-09
+tags: ["notes", "tasks", "reference"]
+ai-disclosure: "generated"
+ai-model: "claude-sonnet-4-5"
+ai-provider: "Anthropic"
+
+---
+
+## Overview
+
+Use `data-task` on list items to convey task state without CSS classes.
+
+```html
+<ul>
+  <li data-task="done">Completed item</li>
+  <li data-task="wip">Work in progress</li>
+  <li data-task="blocked">Blocked item</li>
+  <li data-task="todo">Not started</li>
+</ul>
+```
+
+## States
+
+| Value | Meaning |
+|-------|---------|
+| `done` | Completed — green check |
+| `wip` | In progress — amber |
+| `blocked` | Blocked — red |
+| `todo` | Not started — muted |