For library-wide full-text search (the user's #1 named differentiator):
snippetFor() finds the first case-insensitive match of a query in a source
string (PDF text page / typed box / OCR'd handwriting) and returns a windowed
excerpt centered on it, preserving the match offset + length and
truncatedStart/End flags so the results list can render "…ctx **match** ctx…"
and jump to the hit. The full match is always included; near-edge matches don't
over-truncate. Returns null for empty/absent query.
The FTS index + ranking live in the DB (search_indexer, later); this is the
pure, storage-free excerpt math, fully unit-tested.
flutter analyze lib/editor clean; 164/164 tests (+8).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
