[feat] Improve error message for forbidden paths during dev

[itsMapleLeaf]

Describe the problem

This error message shows in the browser console when an FS operation fails due to a disallowed path:

"forbidden path C:\whatever..."

It turns out I was missing the "fs:allow-exists" permission, but the error message didn't give me any clue about that, and it made me think something elsewhere else was broken 😅

Describe the solution you'd like

The error message should be more specific:

missing the 'fs:allow-exists' permission for this path: C:\whatever...

Alternatives considered

No response

Additional context

No response

[ayangweb]

tauri-apps/plugins-workspace#1927 (comment) This might help.

[itsMapleLeaf]

tauri-apps/plugins-workspace#1927 (comment) This might help.

My issue is already resolved, I'm specifically suggesting to improve an error message I encountered