The status line session_name (plus editor border / gap fill) colors itself with a per-session accent hashed from the name via hslToHex(hue, 0.9, 0.72). The fixed lightness is tuned for dark backgrounds; on light themes high-luminance hues (yellow/lime/cyan) render near-invisible (~1.3:1 contrast). statusLine.sessionAccent (#918) only gates the border/gap fill, not the segment text, so there was no way to make the title legible on a light theme.
Add Theme.isLight (from userMessageBg luminance) and make getSessionAccentHex bisect lightness to cap perceived luminance on light themes, keeping the per-session hue while staying readable. Pass theme.isLight at all four accent call sites; add a unit test.
Refs #918, #680.
Paweł J. Wal
06eb1d709f