open folder always asks which folder

[swimmingbrain]

Open Folder in Firefox and Safari reopened the last project stored in the browser instead of asking. That was the fallback from this morning, and it was the wrong call: a button called Open Folder has to show a folder picker, every time.

What changed

• Browsers without the directory handle api get the folder upload picker instead. The picked folder is copied into a project inside the browser (the same place New Project uses there), so it can be edited, compiled and committed. A toast says it is a copy, and that download or push is how changes get out. node_modules and .git are skipped, so are files over 50 MB.
• Projects that live inside the browser are listed under "In this browser" in the sidebar and on the welcome screen, instead of one of them hijacking the Open Folder button.
• Browsers that can't store projects at all (no createWritable) get the tex and bib files of the picked folder opened as tabs.
• Chrome and Edge are untouched, they had the real picker all along.
• The deploy workflow can be started by hand from the Actions tab, for days like today when GitHub's push events don't reach Actions.

Checked in a browser with the pickers removed: the picker shows, a folder with a chapters subfolder is copied in, main.tex compiles with the chapter in the PDF, the project is listed after a reload, and Open Folder asks again.