Fix electron type to reflect that it could be undefined

[jtran]

The main change here is not making the type of window.electron lie. Instead of being IElectronAPI, this PR changes it to IElectronAPI | undefined. Everything else falls out of that.

• Instead of checking if isDesktop() is truthy, check window.electron. It's natural type narrowing.
• This adds a dependency on https://github.com/chaiNNer-org/node-path so that Windows-aware path functions are available in the web, and there's less error checking.
• Rename fileSystemManager → projectFsManager to make it clear that it's doing everything relative to the project directory. If you don't want this functionality, use fsManager, which is another instance where we don't set the project directory.
• Some functions take an electron parameter but don't use it. This is because they access the filesystem some other way, like fsManager. But they only make sense in Electron. So by requiring an Electron argument, people cannot accidentally call it in the web. You can think of it as providing proof of Electron. If we ever implement another way to store files on the web, like cloud storage, we can remove this parameter.

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[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #8019 will not alter performance

_{Comparing jtran/electron-type (3bfbe86) with main (7235ab4)}

Summary

✅ 89 untouched benchmarks

[jtran]

This lib doesn't have types. Should we find another one?