fts5_cjk — cjk_unicode61 FTS5 tokenizer

unicode61 + CJK character bigrams (Lucene CJKAnalyzer semantics). Fixes 1-2 char Korean/Chinese/Japanese terms falling through to LIKE full-table scans in session search.

Build & install to ~/.hermes/lib/:

./build.sh

Uses the system sqlite3ext.h when available, else the vendored copy in vendor/ — no libsqlite3-dev required.

Once the extension is installed, the next SessionDB open creates the messages_fts_cjk index (external-content, tool rows excluded — same v23 storage discipline as the other indexes). On a populated database, run

hermes sessions optimize-storage

to backfill it; new messages are indexed live either way. Set sessions.cjk_fts: false in ~/.hermes/config.yaml to disable. Override the .so location with HERMES_FTS5_CJK_SO.

Contributed by Soju06 (PR #65544).