webex: boolean attributes can't be conditional

Found in mission 013 (ident), from reading plugins/webex/view.hl: an attribute is always written as name="value", so checked/disabled driven by a member would always be active. Expected: a false member leaves the attribute out. Workaround in ident: buttons with role=switch and "aria-checked" = member (quoted attribute names work), a separate if branch for the locked state.