Update upstream merge scripts to use a generic x-opencode- → x-kilo- regex
that catches all current and future headers automatically. Apply the same
replacement to all source files so the codebase is ready for the next
upstream merge.
Adds test cases for filtering sessions by directory, root sessions only,
start time, search terms, and result limits to ensure the listing
functionality works correctly for all filter combinations.
Catriel Müller