MapViewModel converts MoonPosition.gha into the sub-lunar longitude with
`if (gha <= 180) -gha else 360 - gha`, which is only a valid longitude while gha
stays inside 0..360. Nothing enforced that: getMoonPosition relies on
`while (teg > 360) teg -= 360` reducing GMST before the single
`if (gha < 0) gha += 360` correction, and the raw GMST polynomial is about
3.5e6 degrees today, so losing that one line silently pushes the Moon marker
millions of degrees off the map instead of failing loudly.
Sweep a synodic month at 37-minute steps (1,167 samples) asserting gha stays in
0..360 and the derived longitude in -180..180, plus a check that the hour angle
advances 10-20 degrees per hour.
Verified the test has teeth: deleting the teg reduction makes both cases fail;
with the current implementation :core:domain:test is green. No production change
- the existing code is correct.
mckero
af96fe1cf0