## What happened

A desktop notification whose `app_icon` is a name that doesn't resolve in the
icon theme renders **Qt's broken-image placeholder** (a purple/black checkered
box) in the notification card, instead of hiding the icon slot.

Concretely: Claude Code sends notifications with `app_icon = "claude"`. There is
no `claude` icon in a stock Omarchy icon theme, so every Claude Code notification
shows the placeholder box where the app icon should be.

## Steps to reproduce

```bash
notify-send -a "Claude Code" -i claude "Test" "body"
```

→ notification card shows the purple/black broken-image placeholder in the icon
slot.

```bash
notify-send -a "Claude Code" "Test" "body"     # no -i
```

→ fine, no icon slot, no box.

## Expected

`plugins/notifications/components/NotificationCard.qml` already intends to handle
this — the slot's `visible` binding has a comment:

```qml
// Hide the slot when the icon failed to resolve (themed-icon name
// not in the user's icon theme) AND we don't have a glyph fallback
// — prevents rendering Qt's pink broken-image placeholder.
visible: !root.collapseRedundantIcon && !root.compactGlyph
  && (root.hasSmallIcon || root.hasGlyph)
  && (root.hasGlyph || smallIconImage.status !== Image.Error)
```

So the placeholder box should never be visible. It is.

## Notes / what I tried

- Installing a valid `claude.png` into `~/.local/share/icons/hicolor/{48,64,128,256}x*/apps/`
  + `~/.local/share/pixmaps/claude.png`, running `gtk-update-icon-cache -f`, and
  `omarchy restart shell` — **box persists.**
- The child `Image` (`id: smallIconImage`) has `asynchronous: true` and its own
  `visible: !root.hasGlyph || smallIconImage.status === Image.Ready`. For a
  no-glyph notification (`hasGlyph` false) that resolves to `visible: true` even
  when `status === Image.Error`. Possibly the placeholder paints for a resolved-
  but-unrenderable source, or `status` lands on `Ready` with a null pixmap
  rather than `Error`, so the parent guard never trips.
- Theme is a light Omarchy theme (`color-scheme: prefer-light`), icon theme
  `Yaru-grey`. Quickshell owns `org.freedesktop.Notifications`.

## Environment

Omarchy 4.0.3-1 · Hyprland 0.56.2 · quickshell (Omarchy shell) · ROG Flow X13
GV302XA · kernel 7.2.3

## Suggested fix

Either bundle a `claude` icon (the agents plugin already ships
`plugins/agents/assets/claude.svg`), or make the slot also hide when the image
resolves but fails to paint (treat `status === Image.Ready && !sourceSize`/null
paint like `Error`), so *any* unresolvable/unrenderable `app_icon` collapses the
slot instead of showing the placeholder.