Local file losing a file handler

[FarSeeing]

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Describe the bug When creating a new local (device-saved) diagram it gets opened in a new tab but then when you save that diagram - it gets downloaded on each save

To Reproduce Steps to reproduce the behavior:

1. Go to a secure site (like https://app.diagrams.net/) using modern browser (to utilize window.showOpenFilePicker)
2. Chose to store diagrams on a device
3. Create a diagram selecting some file
4. Modify & save it, verify it's saved silently,
5. Create another diagram using the File → New... menu item
6. Select another file
7. The second diagram gets opened in a new tab
8. Modify that new diagram and save it, verify it gets downloaded

Expected behavior I don't think it's possible to pass a file handler between windows (even same-origin ones) so I would think on changing LocalFile save behavior: if we don't have any file handler (exactly when we have a new tab opened) and the native window.showOpenFilePicker method is supported - call it.

Screenshots If applicable, add screenshots to help explain your problem.

draw.io version (In the Help->About menu of the draw.io editor):

• draw.io version 24.8.1

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Browser Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

I tested the problem in incognito/private mode with all browser extensions switched off, write "yes" below:

• yes

Additional context Add any other context about the problem here.

[FarSeeing]

BTW, FileSystemFileHandle could be passed between tabs but works only for the same-origin tabs.