Each line gets a `channel` inferred in addLine() from its color and any
"[daemon]"/"[xmrig]"/"[app]"/"[rpc]" prefix, which is then stripped. renderOutput draws
a thin colored bar in the existing left margin (padX) per line — node log (blue), mining
(amber), app (teal), rpc (secondary), command (accent), error (red). Drawn in the margin
so it never touches the text layout or selection; filtering is unaffected (it keys off
color, not the prefix).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>