v0.4.1

Minor release. Adds an alternative input source — operators can now
stream directly from a systemd journal unit instead of pointing at a
log file. Useful on setups where log files are not exposed or where
rotation makes the right path hard to pin down. Also includes a
follow-up to the LIVE-70 work that lets the shred-streams snapshot
surface a (peak N) annotation when the chart shows recent err
activity that the last batch sample alone would hide.

Added

• --unit <SERVICE> — stream the log from a systemd journal unit
  instead of a file. Mutually exclusive with the positional log
  path via clap ArgGroup (exactly one must be passed). Spawns
  journalctl via argv-safe Command::args([...]) — no shell
  involved, so operator-supplied unit names cannot inject. The
  child is held in Arc<Mutex<Child>> on TailHandle; Drop
  signals shutdown, kills the child, and waits.

• --since <SPEC> — historical scan window for journal mode.
  Default 10 minutes ago. Accepts anything journalctl --since
  understands (today, yesterday, "1 hour ago", ISO dates).
  Bounds the historical bulk read only; the Live tab tail starts
  following from "now" via journalctl -n 0 -f regardless of the
  --since window.

• LogSource enum (File(PathBuf) / Journal { unit, since })
  in a new crate::source module. runner and live::tail both
  match on it; main builds it from the parsed CLI args.

  Contributed by @schmiatz in #1. Thank you!

Changed

• Shred-streams snapshot in the Live tab appends (peak N) after
  the err field when the visible chart window has seen a batch
  with more errors than the most recent sample (LIVE-70). The
  annotation is suppressed in the steady state, so the line stays
  compact when there is nothing extra to surface. Matches the
  chart's visible-window scale 1:1 via LaneSpark::peak_recent.

Documentation

• README now demonstrates the journal-mode invocation pattern and
  notes that --since controls the historical scan only — the
  Live tab always follows from "now" once tailing starts. Journal
  mode is documented as Linux-only (requires journalctl on
  PATH).