fix: the mark iii lights now switch, and what glows lights the armour

[synaps3s]

The problem

On the live Mark III model the lights control changed almost nothing, and the glow from the reactor, eyes and palms had no presence.

The control only lowered the emission of those parts, which kept their pale blue base and the studio's reflections, so off looked much like on. And the viewer had no bloom, so nothing glowed into the air.

The fix

• Off now means dark. The glass falls to a trace of its colour.
• What glows lights the armour. Each glowing part carries a small lamp of its own, parented to it so it travels when the armour is taken apart.
• Bloom. The light spills into the air around the reactor, the eyes and the palms.
• The canvas stays transparent. The bloom's blur writes full opacity, which painted the whole canvas black. Its light is now added without touching the canvas's alpha, so the panel and the starfield still show through in both themes.
• Only what is switched on blooms. The threshold sits above anything the studio light makes the metal reflect, and the gold has lost its clearcoat.

Checked

npm run validate passes. Opened in a browser with the key: night with the lights on and off, day with the lights on.

Rollback

Merge with a merge commit and keep the branch. Reverting the merge commit returns the viewer to how it is on main now.