Function os_sandbox_active 

pub fn os_sandbox_active(tier: SandboxPolicy, os_enabled: Option<bool>) -> bool

Whether the OS-level backstop is ACTIVE for tier/os_enabled at all — the “turn the sandbox ENUM into an enabled/disabled OS engagement” half of §3.1’s table. DangerFullAccess is an absolute opt-out (never confine, regardless of os_enabled — §3.1 item 1: “no confinement (opt-out)”). Otherwise: an EXPLICIT os_enabled value wins; None (never set — the bare sandbox = "<tier>" shorthand, or a CLI --sandbox flag, neither of which touch the table’s enabled key at all) preserves the PRE-P5-10 trigger this crate already shipped (tools/builtins.rs’s macOS seatbelt firing off ctx.sandbox alone, no separate gate) — so an existing CLI user or the cx-parity preset (bare sandbox = "workspace_write", no enabled key) keeps its current confining behavior byte-for-byte, while cc-parity’s explicit table-form enabled = false (§3.1’s own “OS sandbox OFF… opt-in” comment) is honored as a real, independent off-switch.