separate the law that binds from the discipline that is shown

For an Eastern Catholic church these are sharply different questions and the
library was collapsing them. Ruthenian particular law binds on four kinds of
day in the year; the tradition those parishes actually keep is the Byzantine
fast entire. Reporting only the law made a week of the Great Fast read as
'no meat, fish, eggs or dairy' seven times over, which is the legal floor and
not the fast.

--typikon shows the day at the Typikon's discipline while the obligation
still comes from the jurisdiction's own law, because that is the part only it
can say. The Ruthenian rule now answers 'what binds here' separately from
'how is this day kept', which is what makes the two composable at all.

Three tests hold the seam: exactly the same days bind whichever discipline is
displayed, the binding minimum is never stricter than the level shown, and
the flag is a no-op for a jurisdiction already on the Typikon.

README.md

@@ -136,6 +136,25 @@ binds. A calendar saying "obligatory" where nothing obliges is worse than no
 calendar; one reporting only the binding minimum makes the obligatory days look
 laxer than the voluntary ones beside them.
 
+### The law and the fast are not the same question
+
+For an Eastern Catholic church the two come apart sharply, and reporting only
+the law makes the Great Fast look like four days of abstinence a year. That is
+what binds; it is not what is kept.
+
+```console
+$ typikon -j ruthenian --typikon
+```
+
+shows the day at the Typikon's full discipline while still reporting what your
+own church's law obliges, and still marking it. A week of the Great Fast under
+Ruthenian law is seven days of "no meat, fish, eggs or dairy" with three of
+them starred; the same week at the Typikon's discipline runs from a total fast
+on Clean Monday through xerophagy, wine and oil, and a saint's relaxation, with
+the same three days starred. Nothing about the obligation changes.
+
+It is a no-op for a jurisdiction already reckoning by the Typikon.
+
 Where usages differ (Great Thursday, the Exaltation, Lazarus Saturday), this
 follows the common published rule and names it in the day's reason so you can
 disagree with it. Monastic practice, and the Holy Mountain in particular, is