A Safari import with no Full Disk Access failed with the generic "cookie
database could not be read" instead of telling the user to grant access — and
no prompt appears, because macOS never prompts for Full Disk Access; the app is
added by hand.

The denial arrives as EPERM, which Effect tags `Unknown`, not
`PermissionDenied` (that is EACCES), so checking the tag alone never matched.
The underlying errno is checked too. Verified against the real jar: the reason
is now `needsFullDiskAccess`, which the renderer maps to the System Settings
instruction.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>