fix(setup): repair the projects directory instead of creating it once

[rmyndharis]

Summary

Deleting the default projects folder left the app permanently broken. The editor opened on a folder that was not there — empty explorer, files that could not be saved, terminals starting in a missing directory — and stayed that way through every relaunch and force-stop. The only ways back were clearing app data or installing a new version.

It was created in createDirectories(), whose only caller returns early unless isFirstRun(), and that gates on versionName. So the directory was created once per app version and never looked at again.

Why only this directory

Alone among the ones created there, it lives in app-external storage — /storage/emulated/0/Android/data/<pkg>/files/projects — which shows up in every file manager and is exactly the kind of path a cleaner app removes. The rest are under filesDir, where nothing outside the app can reach them.

So this is not a partial fix. It is the only one that can disappear.

Two call sites, because either alone leaves a hole

• SplashActivity's always-run block covers the launch path, beside the other repairs that exist for this same class of drift.
• MainActivity.loadVSCode ensures it immediately before handing the path to the workbench — that activity can be started directly, and the folder can be deleted while the app is running. The URL-derived branch beside it already refused a path that was not a directory; the default now gets the same care.

isDirectory, not exists

Neither can turn a file into a directory, so the difference is not the outcome — it is whether anyone is told. exists() answers yes to a plain file sitting at that path and returns in silence, handing the workbench something it cannot open with nothing in the log.

Tests, mutation-checked

Mutation	Result
Make the repair a no-op (the state before this change)	2 of 3 fail
Revert isDirectory → exists()	the warning test fails
Unmodified	296 tests, 0 failures

The third test was a tautology on its first draft — it asserted a state that holds either way — and was rewritten to assert the signal, which is the only thing that actually differs. Worth saying because a tautological test passes mutation testing by never having discriminated in the first place.

Fixes #81