The formula checker accepts roll fields a roll effect can't read #267

Area

Engine: the formula checker vs the engine for a roll effect's roll root.

Version

Current main.

Input

A roll effect whose value or when reads roll.total, roll.faces, roll.kept or roll.empty.

Expected

The checker accepts only what the engine binds, so a formula that can't work fails at load.

Actual

The formula checker accepts these names, but the engine binds only item, self and tags for a roll effect (formulas.md now says so). Such a formula loads, then fails when the action runs. Found while fixing the spec docs (#265).