<sidecar_dir>/<id>.events.jsonl holds one session/update notification
per line; seq is the line's 1-based position. open_events returns an
append handle held for the session's lifetime, and terminates a
partial last line first so a hard kill mid-write never glues the next
event onto the fragment. read_events takes a Since (forward, exclusive)
or Before (backward, exclusive, None for the tail) cursor with a limit;
unparseable lines keep their seq and are skipped. delete removes the
log with the sidecar; load_all ignores .jsonl.
Each append is a single write_all to the kernel, no fsync: a killed
daemon loses nothing already written, and an fsync per streamed chunk
is the wrong trade for a log that is not meant to survive power loss.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
