fix(parser): treat special chars as literals in macro attributes

Macro attributes (image, audio, video, icon) now parse `.`, `#`, `%` as literal characters
instead of interpreting them as shorthand syntax.

This matches asciidoctor behavior:
- `image::photo.jpg[Diablo 4 picture of Lilith.]` → trailing period preserved
- `image::photo.jpg[.role]` → ".role" is alt text, not a CSS class
- `image::photo.jpg[Issue #42]` → "#42" is literal, not an ID

Shorthand syntax (.role, #id, %option) remains supported only in block-level attribute
lines (e.g., `[.class]` before a block).

Also consolidates attribute processing logic between block and macro attributes into
shared helper functions.

Author: nlopes

acdc-parser/CHANGELOG.md

@@ -44,6 +44,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- Macro attributes (image, audio, video, icon) now parse `.`, `#`, `%` as literal characters
+  instead of interpreting them as shorthand syntax. This matches asciidoctor behavior where
+  `image::photo.jpg[Diablo 4 picture of Lilith.]` preserves the trailing period in alt text,
+  and `image::photo.jpg[.role]` treats `.role` as literal text, not a CSS class. Shorthand
+  syntax remains supported in block-level attribute lines (e.g., `[.class]` before a block).
 - DSV tables now correctly preserve the first cell. Previously, DSV format (`cell1:cell2`)
   was incorrectly treated like PSV (`| cell1 | cell2 |`), causing the first cell to be
   dropped. Escape handling (`\:` → literal `:`) also works correctly now.