Module meta_guard 

Guard bits stored in MetaSlot::guard (issue #38 : extensible without touching page bytes).

Distinct from frame_flags::POISONED (logical frame state in flags).

Constants

KERNEL_ONLY

Frame must not be exposed as a userspace mapping (kernel / debug).

NONE

No guard condition asserted.

POISONED

Slot marked poisoned after detected corruption (never recycle blindly).