fix(render): a month answers to both spellings of its own name

A week object carries month_name/month_num/month_abbr, because at that
level a bare `name` would be ambiguous. An author who learned those names
inside {{#weeks}} reaches for them one level up inside {{#months}} too --
where they resolved to nothing, and an unknown key renders as the empty
string by design, so the result was a silently blank month heading rather
than any error.

Found by writing a template from scratch rather than copying a shipped
one; every shipped template sidesteps it, which is why nothing caught it.

The aliases are additive, so no existing template or golden changes.
colitur-templates(5) now documents both spellings and says why they
exist.

1 files changed, 19 insertions, 0 deletions

diff --git a/test/test_view.ml b/test/test_view.ml
index b2d302e..a542419 100644
--- a/test/test_view.ml
+++ b/test/test_view.ml
@@ -292,6 +292,25 @@ let test_vocabularies_localise () =
   Alcotest.(check string) "rite_name" "Missale Romanum, editio typica 1962"
     (as_str (get [ "rite_name" ] v))
 
+(* A month answers to BOTH spellings of its own name. The week objects nested
+   inside a month expose [month_name]/[month_num]/[month_abbr], so an author
+   who learned those names there reaches for them one level up too -- and an
+   unknown key renders as the EMPTY STRING by design, so the mistake produced
+   a silently blank heading rather than any error. Found by writing a template
+   from scratch; the shipped ones all sidestep it. *)
+let test_month_answers_to_both_spellings () =
+  let v = view_named 2027 in
+  let jan = List.hd (as_list (get [ "months" ] v)) in
+  let same a b =
+    Alcotest.(check string) (a ^ " = " ^ b) (as_str (get [ a ] jan))
+      (as_str (get [ b ] jan))
+  in
+  same "name" "month_name";
+  same "num" "month_num";
+  Alcotest.(check string) "month_name" "Ianuarius" (as_str (get [ "month_name" ] jan));
+  Alcotest.(check bool) "month_abbr is present and non-empty" true
+    (as_str (get [ "month_abbr" ] jan) <> "")
+
 let suite =
   ( "View",
     [ Alcotest.test_case "year shape" `Quick test_year_shape;