Root cause: Tauri's dragDropEnabled (default: true) intercepts drag events
at the webview level, preventing HTML5 DnD from working for tab reorder
and BlockNote block handle drag. Setting dragDropEnabled: false lets all
drag events flow through the standard DOM API.
Image drops now use the HTML5 drop handler + uploadImageFile (same as
paste-upload) instead of Tauri's onDragDropEvent + copyImageToVault.
Removed the useInternalDragFlag workaround and padding hack.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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