Enable the safe_html5_viewer plugin by default

KPUB_ZIP content has no renderer otherwise.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WAmANyoPp3rQdCNRdQt4k6

Author: rtibbles

kolibri/utils/build_config/default_plugins.py

@@ -8,6 +8,7 @@
     "kolibri.plugins.learn",
     "kolibri.plugins.media_player",
     "kolibri.plugins.pdf_viewer",
+    "kolibri.plugins.safe_html5_viewer",
     "kolibri.plugins.perseus_viewer",
     "kolibri.plugins.qti_viewer",
     "kolibri.plugins.setup_wizard",

packages/kolibri/components/internal/filePresetStrings.js

@@ -24,6 +24,7 @@ const filePresetStrings = {
   slideshow_manifest: 'Slideshow ({fileSize})',
   slideshow_image: 'Slideshow image ({fileSize})',
   bloompub: 'Bloom Pub Document ({fileSize})',
+  kpub: 'Kolibri Article ({fileSize})',
 };
 
 const filePresetTranslator = createTranslator('FilePresetStrings', filePresetStrings);