fix(universe): on a nebula's page a body inside it is named in white over a dark grey copy of its name

[alowpoly]

A star inside a nebula is named over the nebula's picture, in its own color at 65%, lost on its bright parts. On the nebula's own page the name is now white at full strength over a #404040 copy of the same text, one pixel down and right: the name painted twice, with no stroke, shadow or blend. The circle and the name's side are unchanged. A body is marked while the nebula that holds it is selected (prepared-world-context.ts); rules in world-context.css, stated in universe-labels.md. Today that is HD 59088 (NGC 2392) and Eta Carinae (Homunculus Nebula).

Proves the change: share of the name's glyph pixels at WCAG 3:1 or better, Chrome with GPU. Before is the same page with the mark removed, as main draws it.

Name, distance	Before	After
HD 59088, 3.19 ly	0%	67%
HD 59088, 5.82 ly (opening)	0%	81%
HD 59088, 10.6 ly	41%	89%
Eta Carinae, 2.19 ly	0%	48%
Eta Carinae, 3.99 ly (opening)	9%	70%
Eta Carinae, 7.27 ly	56%	89%

Clean: prepared-world-context.test.ts (116), renderer tests (775), typechecks, eslint, check-no-variables.

On the Milky Way page all 24 names, these two included, are drawn at 65% as before.

Limits: not run on other engines or the iPad. No image.

PR rules: titles, PDS4 provenance and ISO plain language.