LaneCard gets agents-install/mcp-sync buttons, integration status
badges, and a sync-base --check button (read-only preflight only — no
merge button, that stays a session/skill action). Settings gets
skills-install and housekeeping (gc) buttons, machine-wide. Two new
routes needed (POST /api/skills/install, POST /api/lanes/gc) since
those two primitives were CLI-only until now.
