Removing #rightrail left a dead 360px grid column that narrowed #main.
Shell grid is now sidebar+main; the topbar ◆ (was Toggle-companion-rail)
now dispatches dross-toggle to open/close the floating bubble. Remaining
.rail-* CSS + chrome.js toggleRail are dead no-ops (minor cleanup later).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>