FTS4 triggers fail when indexed rows are updated or deleted #922

With fts_version="FTS4" and create_triggers=True, updating or deleting an indexed row raises sqlite3.OperationalError: SQL logic error:

from sqlite_utils import Database

db = Database(memory=True)
table = db.table("notes")
table.insert({"id": 1, "text": "alpha"}, pk="id")
table.enable_fts(["text"], fts_version="FTS4", create_triggers=True)
table.update(1, {"text": "beta"})  # sqlite3.OperationalError: SQL logic error

Deleting the indexed row also raises the error. The same update and delete work with fts_version="FTS5". I reproduced this with sqlite-utils 4.2.1, Python 3.12.14 and SQLite 3.53.1 on Windows, and also checked the current db.py at 9c66bafa with the installed support modules.

The generated FTS4 update/delete triggers use the FTS5-style INSERT ... VALUES('delete', ...) command after the content row changes. SQLite's FTS4 external-content documentation instead shows deleting the index entry before the content row changes, with the new entry inserted afterward. This is separate from the iterator issue in #902. Codex assisted with the investigation and checks.