fix(template_formatter): preserve dash separator around empty conditional

When an empty conditional sits between a dot and a dash (e.g. `.{atmos?}-{tag}`),
the left-side dot was kept and the dash before the tag was dropped, producing
`...DDP5.1.TAG` instead of `...DDP5.1-TAG`. Prefer the dash when it is the
right-side separator.

Closes #107

unshackle/core/utils/template_formatter.py

@@ -73,7 +73,9 @@ class TemplateFormatter:
                             has_left = s[0] in ".- "
                             has_right = s[-1] in ".- "
                             if has_left and has_right:
-                                return s[0]  # keep left separator
+                                if s[-1] == "-":
+                                    return s[-1]
+                                return s[0]
                             return ""
 
                         result = re.sub(