calibration: throttle reads rest (0), not full, at the detent

Faithful port of a legacy quirk made harmful by axis routing: _throttleLast
initialized to Center and the lT==0 hold path meant the first poll at rest
compounded 16383*32 -> clamped 32766 = FULL throttle until the lever moved
past the deadzone (under the old routing this held LeftTrigger at 255 -
fire-secondary - from power-on). lT==0 now zeroes like the deadzone branch
and _throttleLast initializes to 0, the sanctioned rest value ResetAll/
ResetThrottle already used. Three regression tests replace the one that
asserted the old behavior.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/RioJoy.Core.Tests/Calibration/AxisCalibratorTests.cs

@@ -128,11 +128,39 @@ public class AxisCalibratorTests
         Assert.Equal(AxisOutputs.Center, cal.Update(Report(x: 0)).X);
     }
 
+    // --- Detent regression (legacy quirk deliberately fixed) -----------------
+
     [Fact]
-    public void Outputs_AreClampedToAxisRange()
+    public void Throttle_FirstPollAtRest_IsZero_NotPinned()
     {
-        // The init-state throttle quirk yields a value far over range on the first
-        // poll at rest; the documented 0..Max clamp guards it.
-        Assert.Equal(AxisOutputs.Max, new AxisCalibrator().Update(Report(throttle: 0)).Z);
+        // Regression: the legacy Center init + detent-hold compounded through the
+        // ×32 rescale and pinned Z at Max on the very first poll at rest — full
+        // reverse on a Centered thumb route, full thrust on a UnipolarPositive one
+        // (Descent). Rest must read 0 with no reset and stay there.
+        var cal = new AxisCalibrator();
+        Assert.Equal(0, cal.Update(Report(throttle: 0)).Z);
+        Assert.Equal(0, cal.Update(Report(throttle: 0)).Z);
+    }
+
+    [Fact]
+    public void Throttle_ReleaseExactlyOntoStart_ReturnsToZero_NoSpike()
+    {
+        // Regression: a release landing exactly on the tracked start (lT == 0)
+        // used to hold the last moving value, which the ×32 rescale turned into a
+        // one-poll full-throttle spike until jitter broke it.
+        var cal = new AxisCalibrator();
+        Assert.Equal(0, cal.Update(Report(throttle: 0)).Z);        // seed start at rest
+        Assert.Equal(16000, cal.Update(Report(throttle: -400)).Z); // pushed halfway
+        Assert.Equal(0, cal.Update(Report(throttle: 0)).Z);        // release onto start
+    }
+
+    [Fact]
+    public void Throttle_SampleAboveRunningMax_ReadsAsRest()
+    {
+        // Samples above the tracked start re-base the auto-range (lT == 0 again)
+        // and must read as rest, not re-enter the legacy hold path.
+        var cal = new AxisCalibrator();
+        cal.Update(Report(throttle: -400)); // power-on with lever pushed: becomes the start
+        Assert.Equal(0, cal.Update(Report(throttle: -100)).Z); // above max → re-based, rest
     }
 }