Running cumulative scrobble total per month for the top 10 artists by play count, one line per artist, 10-color fixed palette. Registers LineController in chart.ts (bar/radar were registered, line wasn't). Built by a background subagent (worktree-isolated), merged in by hand: the agent's worktree branched before monthlyArtistPlays was exposed on ListenerProfile, so it independently re-added the same field — only the LineController registration, the new component, and the +page.svelte wiring were taken; the duplicate field/wiring re-addition was dropped since it already existed on main.