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-frontmatter.md

@@ -0,0 +1,195 @@
+---
+name: frontmatter
+description: Configuration options for individual slides
+---
+
+# Per-Slide Frontmatter
+
+Configuration options for individual slides.
+
+## Layout
+
+```yaml
+---
+layout: center
+---
+```
+
+Available layouts: `default`, `cover`, `center`, `two-cols`, `two-cols-header`, `image`, `image-left`, `image-right`, `iframe`, `iframe-left`, `iframe-right`, `quote`, `section`, `statement`, `fact`, `full`, `intro`, `end`, `none`
+
+## Background
+
+```yaml
+---
+background: /image.jpg
+backgroundSize: cover
+class: text-white
+---
+```
+
+## Click Count
+
+```yaml
+---
+clicks: 5                   # Total clicks for this slide
+clicksStart: 0              # Starting click number
+---
+```
+
+## Transitions
+
+```yaml
+---
+transition: fade            # Slide transition
+---
+```
+
+Or different for forward/backward:
+
+```yaml
+---
+transition: slide-left | slide-right
+---
+```
+
+## Zoom
+
+```yaml
+---
+zoom: 0.8                   # Scale content (0.8 = 80%)
+---
+```
+
+## Hide Slide
+
+```yaml
+---
+disabled: true              # Hide this slide
+# or
+hide: true
+---
+```
+
+## Table of Contents
+
+```yaml
+---
+hideInToc: true             # Hide from Toc component
+level: 2                    # Override heading level
+title: Custom Title         # Override slide title
+---
+```
+
+## Import External File
+
+```yaml
+---
+src: ./slides/intro.md      # Import markdown file
+---
+```
+
+With specific slides:
+
+```yaml
+---
+src: ./other.md#2,5-7       # Import slides 2, 5, 6, 7
+---
+```
+
+## Route Alias
+
+```yaml
+---
+routeAlias: intro           # URL: /intro instead of /1
+---
+```
+
+## Preload
+
+```yaml
+---
+preload: false              # Don't mount until entering
+---
+```
+
+## Draggable Positions
+
+```yaml
+---
+dragPos:
+  logo: 100,50,200,100,0    # Left,Top,Width,Height,Rotate
+  arrow: 300,200,50,50,45
+---
+```
+
+## Image Layouts
+
+```yaml
+---
+layout: image-left
+image: /photo.jpg
+backgroundSize: contain
+class: my-custom-class
+---
+```
+
+## Iframe Layouts
+
+```yaml
+---
+layout: iframe
+url: https://example.com
+---
+```
+
+## Two Columns
+
+```yaml
+---
+layout: two-cols
+---
+
+# Left Side
+
+Content
+
+::right::
+
+# Right Side
+
+Content
+```
+
+## Two Columns with Header
+
+```yaml
+---
+layout: two-cols-header
+---
+
+# Header
+
+::left::
+
+Left content
+
+::right::
+
+Right content
+```
+
+## Full Example
+
+```yaml
+---
+layout: center
+background: /bg.jpg
+class: text-white text-center
+transition: fade
+clicks: 3
+zoom: 0.9
+hideInToc: false
+---
+
+# Slide Content
+```