Physical labels and endpoint bounds
Abstract
Packets ending in negative physical labels
Splitting a physical word at its negative labels preserves every occurrence. When the last label is negative, each resulting block consists of a positive packet followed by one negative label, and there is no tail packet. Empty packets are allowed.
A literal insertion inside a packet moves to its right endpoint by crossing only positive labels. This transport preserves the same old word and all natural prefix bounds; it imposes no symmetry on unequal negative weights. The source-complete packet equivalence and uniform mask allocation are distinct obligations. Unrestricted uniform allocation and full physical J remain open.