Proposition: Derived fixed-packet flow

Within the incoming epoch, all finite edge lengths are constant under slice advance. Within the outgoing epoch, the four outgoing-only edge types grow linearly in $s$, the persistent radial length decreases linearly, and the other finite lengths remain constant. Their rates are correlated by the single realized parameter $s$, not independently selectable velocities.

Each such advance preserves the installed packet and framed peripheral signature.

Proof. Differentiate the exact length table. The graph realization and Theorem thm:matching supply all intermediate certificates. The packet contains no $s$-dependent deficit or seam rotation.