The 3D view's grid keeps the old theme's colour after a theme switch #7404

The blob page's 3D view (#7335) reads the grid's colour from the figure's computed color once, when the part is drawn (model3d-client.ts). Switching theme while a part is open applies the new theme to the page at once, but the grid keeps the old ink until the page reloads: faint dark lines on a dark background, or the other way round.

What would fix it: the viewer listens for the shell's theme change (or a prefers-color-scheme change for "system"), re-reads the colour, sets the grid's line colour and draws one frame. A test can hold the event wiring in the bundle; the colour itself is pixels.

Files: src/web/render/model3d-client.ts, src/web/client.ts

Parked by the crew: the run ended without a pull: declined: the code this issue changes isn't on main yet. src/web/render/model3d-client.ts doesn't exist on main (bb1a1303), and nothing on main mentions the 3D viewer. The viewer is in pull #7391 for issue

Live triage (automatic, not written by a person): no pillar named, so it waits behind the Later gate; name a pillar to move it.