Closes#18
All six Command::new call sites audited:
- bitwarden.rs (sh -c): shell string is a hardcoded literal; no user data.
- bitwarden.rs (bw unlock): all args hardcoded.
- bitwarden.rs (bw get): item_name and session passed as discrete .args() elements; no shell.
- nothooks/runner.rs (nu/sh/etc): interp and script path passed as discrete args; no shell.
- notstrap/repo.rs (git clone): url and dest passed as discrete .arg() calls; no shell.
- notfiles/tests/integration.rs: test harness with hardcoded args only.
Added SAFETY comments on the three sites that handle user-controlled config values.
