Kills the hover/move lag on dense maps. Root causes were in the live
mouse/render path, not the layout:
- Render coalescing: _artMapRender() now just requests a single rAF; the actual
draw (_artMapDraw) runs at most once per frame. A burst of mousemove/pan/
animation calls no longer triggers many full-buffer blits per second.
- Tooltip de-churn: only rebuild the tooltip innerHTML (and reload its image)
when the hovered artist changes; a plain mousemove just repositions. Was
rebuilding innerHTML + a new <img> every pixel of movement.
- Spatial-grid hit-test: bucket nodes into a coarse world grid and test only the
cell under the cursor, instead of sorting + scanning every node each move.
Grid rebuilds only when the node set changes.
- Constellation lines: draw all connection lines as ONE solid-stroke path
instead of creating a fresh linear-gradient object per line every frame —
that per-frame gradient churn was the main 'connected lines' lag.
No layout/data/click changes; behaviour identical, just frame-bound. Pure
frontend; JS syntax clean.
14388d4f42
