Normalize both the candidate and terminal.cwd before the remote-POSIX
containment check so `{cwd}/../other/...` lexical escapes are rejected, and
restore the blocked-system-root gate BELOW the home-directory allow-list in
both resolve_trusted_workspace() and validate_workspace_to_add() so valid
systemd-homed paths under /var/home/... stay allowed. Also normalize POSIX
shapes at the source (_as_posix_path) so every downstream block probe is
shape-consistent (/etc/../home/user -> /home/user).
Co-authored-by: rodboev <rodboev@users.noreply.github.com>