Single purpose description

opfs-finder has one purpose: to let you view and manage the Origin Private
File System (OPFS) of the website in the current tab, through a familiar
Finder-style window. When you click the toolbar button, it opens a file
browser for that one site's private storage, where you can browse, preview,
rename, move, copy, and delete files. It does nothing else — no tracking, no
network requests, no access to page content or other tabs.

Why activeTab is needed

activeTab lets the extension act only on the tab you are currently looking
at, and only when you click the toolbar button. opfs-finder needs this to
know which site's Origin Private File System (OPFS) to open, since OPFS is
scoped per origin. Without activeTab it cannot tell which site's files to
show. It does not read page content, and it never runs on tabs you have not
explicitly activated by clicking the button.

Why scripting is needed

scripting lets the extension inject its file-browser interface into the
active tab after you click the toolbar button. This is required because OPFS
can only be reached from a script running in the page's own origin — there
is no extension API to read another origin's OPFS directly. The injected
script renders the Finder window and performs the file operations you request
within that single tab. Nothing is injected until you click, and nothing runs
in the background.