feat: publish HoloLake model-native living system source

product-source/hololake-platform/site/guides/use-media-previews.md

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+# Use Media Previews
+
+Media previews let you inspect vault files without leaving HoloLake Era.
+
+## Open A File
+
+Select an image, PDF, media file, or unsupported file from a folder or file list. HoloLake Era opens supported files in the app and offers an external-open action for files that should use the system default app.
+
+## All Notes Visibility
+
+Open Settings to choose whether non-Markdown files appear in All Notes:
+
+- PDFs.
+- Images.
+- Unsupported files.
+
+Folder browsing still shows files in their folders even when a category is hidden from All Notes.
+
+## Attachments
+
+When you paste or drop an image into a note, HoloLake Era copies it into the vault and references the copied file from Markdown.
+
+## Troubleshooting
+
+If a preview does not render, open the file in the default app to confirm the file is valid, then check whether the file is inside the active vault and not blocked by operating-system permissions.