feat: polish theme tooling, diagnostics and launcher workflows

Expand the theme editor with multi-select, snapping, context menus, draft
recovery and export validation; add theme backups and trust prompts. Add
in-app diagnostics and rotating log bundle viewing, hardware-accelerated
theme video playback on macOS, and refresh the settings, setup wizard and
theme gallery layouts.

src/lib/components/ui/context-menu/context-menu-item.svelte

@@ -0,0 +1,27 @@
+<script lang="ts">
+  import { cn } from '$lib/utils.js';
+  import { ContextMenu as ContextMenuPrimitive } from 'bits-ui';
+
+  let {
+    ref = $bindable(null),
+    class: className,
+    inset,
+    variant = 'default',
+    ...restProps
+  }: ContextMenuPrimitive.ItemProps & {
+    inset?: boolean;
+    variant?: 'default' | 'destructive';
+  } = $props();
+</script>
+
+<ContextMenuPrimitive.Item
+  bind:ref
+  data-slot="context-menu-item"
+  data-inset={inset}
+  data-variant={variant}
+  class={cn(
+    "focus:bg-accent focus:text-accent-foreground data-[variant=destructive]:text-destructive data-[variant=destructive]:focus:bg-destructive/10 dark:data-[variant=destructive]:focus:bg-destructive/20 data-[variant=destructive]:focus:text-destructive data-[variant=destructive]:*:[svg]:text-destructive focus:*:[svg]:text-accent-foreground gap-1.5 rounded-md px-1.5 py-1 text-sm data-inset:pl-7 [&_svg:not([class*='size-'])]:size-4 group/context-menu-item relative flex cursor-default items-center outline-hidden select-none data-disabled:pointer-events-none data-disabled:opacity-50 [&_svg]:pointer-events-none [&_svg]:shrink-0",
+    className
+  )}
+  {...restProps}
+/>