fix(isc): any_character primitive, stray identifiers in rule_line

- Add any_character as an item_atom (matches any single char)
- rule_line now accepts comment_item (comments + stray identifiers)
  inside parallel/sequence blocks

Verification: 278/289 (96.5%), 9 ISC fail.

Author: ronaldtse

lib/interscript/isc/grammar/concerns/items.rb

@@ -14,6 +14,7 @@ module Items
             quoted_string |
               str("none").as(:none) |
               zero_width_primitive |
+              any_character |
               any_constructor |
               capture_constructor |
               maybe_constructor |
@@ -48,6 +49,11 @@ module Items
             ).as(:primitive)
           end
 
+          # any_character — matches any single character.
+          rule(:any_character) do
+            str("any_character").as(:any_char)
+          end
+
           rule(:any_constructor) do
             str("any") >> str("(") >> whitespace? >>
               (range_arg | set_arg | alias_arg).as(:any) >>
@@ -114,7 +120,8 @@ module Items
               str("none") | str("boundary") | str("line_start") |
               str("line_end") | str("word_boundary") |
               str("downcase") | str("upcase") | str("title_case") |
-              str("capture") | str("maybe") | str("some") | str("ref")
+              str("capture") | str("maybe") | str("some") | str("ref") |
+              str("any_character")
           end
 
           # Concatenation: one or more atoms. The continuation pattern

lib/interscript/isc/grammar/concerns/stages.rb

@@ -62,7 +62,7 @@ module Stages
           end
 
           rule(:rule_line) do
-            whitespace? >> rule >> whitespace?
+            whitespace? >> (rule | comment_item) >> whitespace?
           end
 
           # A rule is either compact form (single line) or block form