ADR-0016 Floor ground and emission origin are two different grounds
#Context
ADR-0015 derived a Scope's ground from its stacking context and made it both the floor-check reference and the origin emission is measured from. Its own four-sided acceptance test refuted it: measuring overlay emission from the scrim composite makes the scrim cost zero — the free occlusion ADR-0014 was written to eliminate — and inverts the economics so the legal overlay (mostly readable sheet) costs 0.914 while the violating one costs less. The four required numbers are simultaneously satisfiable only if emission keeps its origin at the theme substrate. The word "ground" was carrying two jobs.
#Decision
The two jobs split. Emission is measured from the theme substrate in every stacking context, without exception — the origin ADR-004 defined, unchanged; the scrim remains chrome and costs the change it makes to the pixels beneath, per ADR-0014. The substrate-floor check verifies the rendered modal ground against a ground derived from the declared stacking context — base and raised predict the theme substrate, overlay predicts the scrim composite computed from shipped tokens — within platform tolerance. A mis-declaration fails because the pixels will not match the prediction; a legitimate overlay passes because they will. No Scope carries a numeric ground; the enumerated stacking context remains the entire declaration surface.
#Rejected options
ADR-0015 as written (one derived ground for both jobs). The superseded decision. Rejected by measurement: it zeroes the scrim's cost and fails its own acceptance test on two of four sides, deterministically.
Exempt overlay Scopes from the floor check. Rejected in ADR-0015 and still rejected: an exemption keyed to a declaration is the laundering path with a context name as the key. The split keeps the audit on overlays — they are held to the ground their declaration predicts.
Raise the modal-inference tolerance. Still rejected: 0.031 against 0.05 leaves no room, and diluting every scene to excuse one case blinds the check.
#Consequences
The engine carries two ground concepts with distinct names in code and receipts: emission origin (theme substrate, invariant) and floor prediction (context-derived). 06-overlay-violation is the acceptance test with all four sides binding, including that its emission failure stands at its recorded value. The Scope contract in packages/core is unchanged — stacking context was already required. ADR-0015's register rows read Superseded; its file is not edited. Touches the substrate-floor row's method; emission and salience rows unchanged.