A.2.6:7.6 - Δ‑Operations (Widen, Narrow, Refit)

• Δ‑G+ (widen). Monotone expansion: S proper-subset S-prime. Every added slice requires direct support under the receiving use; a Bridge and affirmative translation-use claim can define a mapping but supply no such support by themselves.
• ΔG− (narrow). Monotone restriction: S′ ⊂ S. Often used to remove areas invalidated by new findings.
• Refit. A different expression or parameterization designates the same extensional scope after normalization (for example, changing units or factoring common predicates). Refit MUST NOT alter membership and does not create another scope value.

Refit (normalization). A refit MUST preserve membership exactly: extension_RS(S_after) = extension_RS(S_before), so both expressions designate the same scope value. Any change that alters boundary inclusion through rounding, unit conversion, or discretization is a ΔG± change, not a refit.

Edition triggers. A changed extension identifies a different scope value. A changed predicate expression with the same exact extension preserves the scope value but is a content change in the declaration or claim-bearing episteme that carries the expression; its direct governor decides whether another episteme edition is needed.

Discriminating cases. Under one effective reference scheme, 20 °C <= temperature <= 30 °C and the exactly converted 293.15 K <= temperature <= 303.15 K have the same extension and can be related as a refit while designating the same scope. Replacing the inclusive upper boundary with temperature < 30 °C removes every slice exactly at 30 °C; that one membership-boundary change identifies another scope rather than a refit.