Make blocked-off hexes from stars green

If they're red, and sensors overlap the star, then the sensor range turns red, too. Stars are visible at any distance, and nothing can be inside a star, so making them green would be accurate.

Hmm, though it doesn't always happen, and then it would look like you could move into the stars...

The issue names no files, tests, or entry points; start by locating the code that colors blocked-off hexes, sensor ranges, and stars in the Space Empires V mod. Check how overlapping sensors and star visibility are handled, and consider the stated risk that green hexes could appear movable; done means the coloring is accurate without implying movement into stars.

Written by the indexing model from the issue text.