Covers the journal tail: replay what is logged then follow appends, detect a fresh session rewriting the log in place, signal caught-up exactly once, and follow the journal into its archive so the ending's lines arrive exactly once — never replayed, never lost, even when the archive shows up late.

## Before writing SPEC.md files

Read https://raw.githubusercontent.com/brillout/sdd/refs/heads/main/sdd.md
