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, 30 insertions, 4 deletions

diff --git a/man/colitur-templates.5 b/man/colitur-templates.5
index e04560b..e668b55 100644
--- a/man/colitur-templates.5
+++ b/man/colitur-templates.5
@@ -566,13 +566,21 @@ template iterates over directly, without going through
 .BR months .
 .SS month
 .TP
-.B num
-The month number, 1 through 12, as a string.
+.BR num ", " month_num
+The month number, 1 through 12, as a string. The two spellings are the same
+value \(em see the note at the end of this subsection.
 .TP
-.B name
+.BR name ", " month_name
 The month's own resolved display name in the active language (e.g.
 .RB \(lq Ianuarius \(rq ),
-a plain string.
+a plain string. Both spellings are the same value.
+.TP
+.B month_abbr
+The month's abbreviated name in the active language (e.g.
+.RB \(lq Ian \(rq ),
+from the language file's own
+.B [month_abbr]
+section.
 .TP
 .B days
 This month's own
@@ -587,6 +595,24 @@ last rows padded with blank cells (see
 .B day \(->  in_month
 below) so every row has seven entries regardless of which weekday the month
 starts or ends on.
+.PP
+.B "Why two spellings."
+A
+.B week
+object (below) carries
+.BR month_name ", " month_num " and " month_abbr,
+because at that level a bare
+.B name
+would be ambiguous. An author who learned those names inside
+.B {{#weeks}}
+naturally reaches for them one level up, inside
+.BR {{#months}} .
+Before colitur 0.9 they resolved to nothing there, and because an unknown
+key renders as the EMPTY STRING by design (see
+.B SCOPE AND LOOKUP
+above), the result was a silently blank month heading rather than any
+error. A month now answers to both. Prefer the short forms in new
+templates: a month is the only scope where they are unambiguous.
 .SS week
 .TP
 .B num