Out with the old, and in with the new...
Having fixed the ground problem with my headlights this morning, I now suspect that it was just a loose connection to the old tree rather than the tree itself, but nonetheless, replacing the one on the left with the one on the right can't possibly have been a bad idea.
Some days here in this Vanagonsphere, when you least expect it, things just sort of flow. I rose shortly after seven this morning, had a leisurely cup of joe beside the bay before tearing into the above, and then made the necessary adjustments to the sliding door so that it would stop opening anytime I went over a moderate bump. After putting all my tools away and cleaning up, I checked the time and couldn't believe that it wasn't even 10:30 yet. Early birds and worms, folks, early birds and worms.
So I celebrated with a nap. As any seasoned handyman would.