Keep the personal half of the desktop in one place, and ask before installing it

Agent instructions, skills, SSH host aliases and expansion triggers are worth
having identical on every machine one person owns, and belong in none of the
shared configuration. They live in user/ now, with a manifest saying where each
piece goes and a link-user stage that puts it there.

That stage does nothing unless the machine said yes. Somebody who clones Panama
to try the desktop keeps their own ~/.claude/CLAUDE.md exactly where it was;
the question names the destinations and defaults to no. Anything displaced goes
to config/old rather than being deleted.

~/.claude/CLAUDE.md and ~/.codex/AGENTS.md were byte-identical copies of one
file, which is the drift this exists to prevent.

Also adds the vitals toggles for the battery and Claude usage readouts, which
had preferences and no way to reach them.

user/agents/skills/slidev/references/core-layouts.md

@@ -0,0 +1,286 @@
+---
+name: layouts
+description: Available layouts for slides
+---
+
+# Built-in Layouts
+
+Available layouts for slides.
+
+## Basic Layouts
+
+### default
+
+Standard slide layout.
+```yaml
+---
+layout: default
+---
+```
+
+### center
+
+Content centered horizontally and vertically.
+```yaml
+---
+layout: center
+---
+```
+
+### cover
+
+Title/cover slide with centered content.
+```yaml
+---
+layout: cover
+---
+```
+
+### end
+
+End slide.
+```yaml
+---
+layout: end
+---
+```
+
+### full
+
+Full-screen content, no padding.
+```yaml
+---
+layout: full
+---
+```
+
+### none
+
+No layout styling.
+```yaml
+---
+layout: none
+---
+```
+
+## Text Layouts
+
+### intro
+
+Introduction slide.
+```yaml
+---
+layout: intro
+---
+```
+
+### quote
+
+Large quotation display.
+```yaml
+---
+layout: quote
+---
+```
+
+### section
+
+Section divider.
+```yaml
+---
+layout: section
+---
+```
+
+### statement
+
+Statement/affirmation display.
+```yaml
+---
+layout: statement
+---
+```
+
+### fact
+
+Fact/data display.
+```yaml
+---
+layout: fact
+---
+```
+
+## Multi-Column Layouts
+
+### two-cols
+
+Two columns side by side:
+```md
+---
+layout: two-cols
+---
+
+# Left Column
+
+Left content
+
+::right::
+
+# Right Column
+
+Right content
+```
+
+### two-cols-header
+
+Header with two columns below:
+```md
+---
+layout: two-cols-header
+---
+
+# Header
+
+::left::
+
+Left content
+
+::right::
+
+Right content
+```
+
+## Image Layouts
+
+### image
+
+Full-screen image:
+```yaml
+---
+layout: image
+image: /photo.jpg
+backgroundSize: cover
+---
+```
+
+### image-left
+
+Image on left, content on right:
+```yaml
+---
+layout: image-left
+image: /photo.jpg
+class: my-class
+---
+
+# Content on Right
+```
+
+### image-right
+
+Image on right, content on left:
+```yaml
+---
+layout: image-right
+image: /photo.jpg
+---
+
+# Content on Left
+```
+
+Props: `image`, `class`, `backgroundSize`
+
+## Iframe Layouts
+
+### iframe
+
+Full-screen iframe:
+```yaml
+---
+layout: iframe
+url: https://example.com
+---
+```
+
+### iframe-left
+
+Iframe on left, content on right:
+```yaml
+---
+layout: iframe-left
+url: https://example.com
+---
+
+# Content
+```
+
+### iframe-right
+
+Iframe on right, content on left:
+```yaml
+---
+layout: iframe-right
+url: https://example.com
+---
+
+# Content
+```
+
+## Layout Loading Order
+
+1. Slidev default layouts
+2. Theme layouts
+3. Addon layouts
+4. Custom layouts (`./layouts/`)
+
+Later sources override earlier ones.
+
+## Custom Layouts
+
+Create `layouts/my-layout.vue`:
+
+```vue
+<template>
+  <div class="slidev-layout my-layout">
+    <slot />
+  </div>
+</template>
+
+<style scoped>
+.my-layout {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+</style>
+```
+
+With named slots:
+
+```vue
+<template>
+  <div class="slidev-layout two-areas">
+    <div class="top">
+      <slot name="top" />
+    </div>
+    <div class="bottom">
+      <slot />
+    </div>
+  </div>
+</template>
+```
+
+Usage:
+```md
+---
+layout: two-areas
+---
+
+::top::
+
+Top content
+
+::default::
+
+Bottom content
+```