App 2.10.1: show negative usage while recuperating

Net regeneration over the window (or the trip) used to hide both
estimates behind "needs a few minutes of driving". It is a real
reading: the usage now shows as negative kWh/100 km, and the range as
"> 999 km" with "while recuperating" beneath it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QLJfZQZeAKAwSqViTmLzki

app/src/test/java/com/evsuite/abrp/RangeEstimatorTest.java

@@ -110,6 +110,9 @@ public class RangeEstimatorTest {
 
         RangeEstimator downhill = new RangeEstimator();
         for (long t = 0; t <= 240_000; t += 2_000) downhill.add(t, -5f, 80f);
-        assertNull("net regeneration", downhill.average(25.4, 240_000));
+        RangeEstimator.Estimate regen = downhill.average(25.4, 240_000);
+        assertNotNull("net regeneration is a reading", regen);
+        assertEquals(-6.25, regen.kwhPer100Km, 0.01);
+        assertTrue(Double.isInfinite(regen.rangeKm));
     }
 }