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-trigger.svelte

@@ -0,0 +1,17 @@
+<script lang="ts">
+  import { cn } from '$lib/utils.js';
+  import { ContextMenu as ContextMenuPrimitive } from 'bits-ui';
+
+  let {
+    ref = $bindable(null),
+    class: className,
+    ...restProps
+  }: ContextMenuPrimitive.TriggerProps = $props();
+</script>
+
+<ContextMenuPrimitive.Trigger
+  bind:ref
+  data-slot="context-menu-trigger"
+  class={cn('select-none', className)}
+  {...restProps}
+/>