Added integration tests for the roam link replacement functionality
to validate the performance optimization that limits the scope of
link replacement by searching specifically for "[[roam:" instead
of any org link bracket pattern. The tests ensure:
1. Special regex characters in buffer content don't break the
search functionality when using search-forward
2. Only roam: links are processed, not other link types like
file: or https:
These tests validate the optimization maintains correctness while
improving performance by avoiding unnecessary replacement attempts
on non-roam links.
Ref: fc8638759b
Ref: 89dfaef38b
