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/session.md

@@ -0,0 +1,67 @@
+---
+title: "Session Log"
+description: "Structured session and activity logs with timestamp, actor, and event semantics."
+section: notes
+prev-url: "diff/"
+prev-title: "Diff"
+next-url: ""
+next-title: ""
+type: notes
+date: 2026-04-09
+tags: ["notes", "session", "reference"]
+ai-disclosure: "generated"
+ai-model: "claude-sonnet-4-5"
+ai-provider: "Anthropic"
+
+---
+
+## Overview
+
+Use `data-role="session-log"` on an `<ol>` to render a structured activity or session log. Each `<li>` is one event.
+
+```html
+<ol data-role="session-log">
+  <li>
+    <time datetime="2026-04-09T08:31:00Z">08:31</time>
+    <span data-actor="vigilio">vigilio</span>
+    <span data-event="wake">Session started — model claude-sonnet-4-6</span>
+  </li>
+  <li>
+    <time datetime="2026-04-09T08:32:14Z">08:32</time>
+    <span data-actor="vigilio">vigilio</span>
+    <span data-event="read">Read vault overview and daily note</span>
+  </li>
+  <li>
+    <time datetime="2026-04-09T08:47:00Z">08:47</time>
+    <span data-actor="system">system</span>
+    <span data-event="commit">Committed: feat(vault): add session-log pattern</span>
+  </li>
+</ol>
+```
+
+## Attributes
+
+| Attribute | Element | Meaning |
+|-----------|---------|---------|
+| `data-role="session-log"` | `<ol>` | Activates session-log layout |
+| `data-actor` | `<span>` | Who performed the action — styled by value |
+| `data-event` | `<span>` | Event type — `wake`, `read`, `write`, `commit`, `sleep` |
+
+## Actor Variants
+
+```html
+<span data-actor="vigilio">vigilio</span>   <!-- agent — primary colour -->
+<span data-actor="ludo">ludo</span>         <!-- operator — accent colour -->
+<span data-actor="system">system</span>     <!-- system — muted -->
+```
+
+## Compact Form
+
+For dense logs, omit the actor and let timestamp + event carry the entry:
+
+```html
+<ol data-role="session-log" data-density="compact">
+  <li><time datetime="2026-04-09T09:00:00Z">09:00</time> <span data-event="wake">Wake</span></li>
+  <li><time datetime="2026-04-09T09:31:00Z">09:31</time> <span data-event="sleep">Sleep — context limit reached</span></li>
+</ol>
+```