Replace complex title processing (9 lines) with single-line title filter approach.
Changes:
- Simplify $admonitionTitle definition from 5 variables to 1 line
- Remove $titleClass conditional logic (4 lines)
- Replace dynamic CSS class with static "grow" class
- Use Hugo title filter instead of CSS capitalize
- Remove TrimSpace processing per author feedback
This maintains the same visual behavior while significantly reducing code complexity.
Related: PR #2704 feedback from ZhenShuo2021