The Logger only live-broadcasts; an output panel opening late would see no
history. LogRing is a drop-oldest sink (default 2000 records) that keeps the
recent window plus per-source and per-level bookkeeping — distinct sources
for the panel's filter dropdown, level counts for the status-bar health
badge. Flutter-free; the dock UI wraps it. First slice of the D-87 dock.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>