Refactor buffer trimming logic to use dynamic line counts (_lines per entry)
against PAD_SIZE (10k) instead of fixed entry count (MAX_BUFFER_SIZE=200). This
prevents premature cleanups for short messages, reduces scrolling disruptions
during history loads, and scales better with rendered content size.
Delete oldest/newest entry from opposite end only when total lines approach
ncurses pad limit, minimizing unnecessary deletions.
Simplify overflow warning log by removing unused MAX_BUFFER_SIZE reference.
Update buffer.c header for improved DX:
- Add detailed module overview explaining role (in-memory UI buffer vs. DB
persistence), key features (trimming, metadata), and integration (ncurses).
- Shorten copyright/license boilerplate to concise pointer (LICENSE ref).
- Add fork notice; preserve original copyrights per GPLv3.
Partially addresses #36 (stuck scroll mitigation via fewer cleanups)
Related to #36
