Function shell_sandbox_unenforceable 

pub fn shell_sandbox_unenforceable(
    policy: SandboxPolicy,
    platform: &str,
    tools_enabled: &[&str],
    landlock_available: bool,
) -> bool

True when the requested sandbox policy cannot be enforced for shell subprocesses: a confining policy, a platform without an OS sandbox primitive wired up (only macOS/seatbelt is, via sandbox-exec), and at least one shell tool ("bash" or "shell") enabled.

This is a pure function so it’s mechanically testable on any host OS: callers pass the platform (typically std::env::consts::OS) and the set of enabled tool names rather than relying on cfg!/target_os. It does not itself sandbox anything — it only tells embedders/CLIs whether the gap documented on SandboxPolicy applies right now, so they can warn. P5-10 (§2 module 12): landlock_available is the caller’s REAL Linux Landlock-availability probe (crate::sandbox::landlock_available(), typically) — a PARAMETER, not an internal cfg!/probe call, same “pure, mechanically testable” contract this function already had. Before P5-10, platform == "linux" always meant “unenforceable” (no OS primitive existed yet); now it means “unenforceable UNLESS Landlock is actually available on this kernel” — a confining tier on a Landlock-capable Linux box is REAL enforcement, not a gap, so this must say false for it (never claim a gap that no longer exists). platform == "macos" is unconditionally false regardless of this parameter (seatbelt, a separate primitive, always exists there); every other platform (including platform == "linux" with landlock_available == false) is unaffected by this parameter and keeps the pre-P5-10 “no primitive” answer.