feat(launcher): restore Kill Apps button in Native OS config

Kills the standard conference presentation app set between sessions:
Microsoft PowerPoint, Keynote, Adobe Acrobat Reader DC, VLC, soffice.

- Calls native.kill_processes({ process_name_li }) via existing relay
- Process list overridable per device via event_device.other_json.launcher.kill_process_li
- Button lives in Native OS config > System Actions (edit mode only)
- Reuses system_status for feedback — shows which apps are being killed
- Original list recovered from git history of legacy architecture docs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/routes/events/[event_id]/(launcher)/cfg_components/launcher_cfg_native_os.svelte

@@ -17,7 +17,8 @@ import {
     RefreshCw,
     SkipBack,
     SkipForward,
-    Square
+    Square,
+    XCircle
 } from '@lucide/svelte';
 interface Props {
     on_expand?: () => void;
@@ -69,6 +70,27 @@ async function handle_display_mode(mode: 'extend' | 'mirror') {
     setTimeout(() => (system_status = ''), 4000);
 }
 
+// Process names sent to kill_processes() when the operator hits "Kill Apps".
+// Covers the standard conference presentation app set — PowerPoint, Keynote, Acrobat, VLC, LibreOffice.
+// Override per device via event_device.other_json.launcher.kill_process_li.
+const DEFAULT_KILL_LIST = [
+    'Microsoft PowerPoint',
+    'Keynote',
+    'Adobe Acrobat Reader DC',
+    'VLC',
+    'soffice'
+];
+
+async function handle_kill_apps() {
+    const native_device = ($ae_loc as any).native_device ?? null;
+    const process_name_li: string[] =
+        native_device?.other_json?.launcher?.kill_process_li ?? DEFAULT_KILL_LIST;
+    system_status = `Killing: ${process_name_li.join(', ')}...`;
+    await native.kill_processes({ process_name_li });
+    system_status = 'Kill signal sent';
+    setTimeout(() => (system_status = ''), 4000);
+}
+
 // Modal state for dangerous actions
 let show_power_confirm = $state<{ action: string; label: string } | null>(null);
 </script>
@@ -240,6 +262,16 @@ let show_power_confirm = $state<{ action: string; label: string } | null>(null);
                             disabled={!$ae_loc.site_header_image_path}>
                             <Image size="0.85em" class="mr-1 shrink-0" /> Reset Wallpaper
                         </button>
+                        <!-- Kill running presentation apps — PowerPoint, Keynote, Acrobat, VLC, LibreOffice.
+                             Use between sessions to ensure a clean slate. List is overridable via
+                             event_device.other_json.launcher.kill_process_li. -->
+                        <button
+                            type="button"
+                            onclick={handle_kill_apps}
+                            class="btn btn-xs preset-tonal-error hover:preset-filled-error-500 justify-start"
+                            title="Kill presentation apps: {DEFAULT_KILL_LIST.join(', ')}">
+                            <XCircle size="0.85em" class="mr-1 shrink-0" /> Kill Apps
+                        </button>
                     </div>
                 </div>
                 <div class="flex flex-col gap-1">